How can I visually tell the difference between a cylindrical and mortise lock?

A cylindrical lock has a round rose or escutcheon plate on the door face, with the lock mechanism contained in a cylindrical body that passes through the door. A mortise lock has a rectangular face plate on the door edge, with the lock body recessed into a pocket (mortise) in the door. When the door is open, you can see the rectangular edge of the mortise case in the door edge.

Why is a 161 prep called 'Turtle Prep'?

The 161 cylindrical prep has a large round cross bore on the door face and a smaller round edge bore, creating a profile that some in the industry compare to a turtle shape. CDF training materials use this visual reference to help specifiers quickly distinguish cylindrical preps from the rectangular mortise pocket of an 86 prep.

Is one lock type better than the other?

Neither type is universally better. Cylindrical locks are less expensive, easier to install, and suitable for most standard commercial applications. Mortise locks offer more functions, higher security, and greater durability in high-traffic environments. The choice depends on the application, security requirements, traffic level, and budget.

What happens if I order a door with a cylindrical prep but the building has mortise locks?

The door cannot accept the mortise locks. A mortise lock requires a rectangular pocket in the door edge that is not present in a cylindrical prep. A new door with the correct 86 mortise prep must be ordered. The original door cannot be field-modified to accept a mortise lock without compromising its structural integrity and voiding any fire rating.

Do fire-rated doors support both cylindrical and mortise locks?

Yes, fire-rated doors are available with either 161 cylindrical or 86 mortise preps. However, the specific lock model must be listed for use on fire-rated assemblies at the required rating — 20-minute, 45-minute, 60-minute, 90-minute, or 180-minute. The correct prep type must be specified at the time of order because the door is manufactured with the prep in place.

What is the difference between masonry and drywall anchors for door frames?

Masonry anchors are designed to fasten frames to concrete block, brick, or poured concrete walls. Drywall anchors are designed for steel stud and gypsum board partitions. Each anchor type distributes loads differently based on the wall material's strength characteristics. Using the wrong anchor type compromises the frame's structural connection to the wall.

When should compression anchors be used instead of TA anchors?

Compression anchors (also called expansion anchors) are typically used in existing masonry openings where the frame is installed after the wall is built. TA (through-anchor) anchors are used when the frame is set in place before the wall is built up around it. The installation sequence determines which anchor type is appropriate.

What happens if the wrong anchor type is installed?

The wrong anchor type can result in a frame that loosens over time, does not pass inspection, or fails under load. In fire-rated openings, incorrect anchoring can void the fire rating because the frame-to-wall connection is part of the tested assembly. Correction typically requires removing the frame and reinstalling with the correct anchors.

Are wire anchors acceptable for commercial door frames?

Wire anchors (also called masonry wire anchors) are used to anchor frames in masonry walls during new construction. They are embedded in the mortar joints as the wall is built up around the frame. Wire anchors are appropriate only for new masonry construction and are not suitable for existing walls or drywall partitions.

Does the anchor type affect fire-rated assembly compliance?

Yes. Fire-rated assembly listings specify the required anchor type and spacing. Using a different anchor type or spacing than what is listed can void the fire rating. For fire-rated openings with 20-minute, 45-minute, 60-minute, 90-minute, or 180-minute ratings, the anchoring system must match the listing exactly.

Which openings require fire-rated assemblies?

Openings in fire-rated wall assemblies require fire-rated door assemblies. Common locations include corridor walls, stairwell enclosures, elevator shaft enclosures, mechanical room walls, and occupancy separation walls. The specific requirements depend on the building code, occupancy type, and wall fire-resistance rating.

What fire ratings are required for corridor walls?

Corridor wall fire-rating requirements vary by occupancy type and building code. Common requirements include 20-minute assemblies for office corridors and up to 60-minute or 90-minute assemblies for healthcare and institutional facilities. The project's code analysis or fire protection engineer determines the specific requirement for each opening.

What happens during inspection if a non-fire-rated assembly is found in a fire-rated opening?

The Authority Having Jurisdiction (AHJ) will issue a code violation requiring the non-compliant assembly to be replaced with a properly rated one. The building may not receive a certificate of occupancy until all fire-rated openings are compliant. This applies to assemblies at all fire-rating levels: 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute.

Can a fire rating be added to an existing non-fire-rated assembly?

No. Fire ratings cannot be added in the field. A fire-rated assembly must be manufactured, labeled, and installed as a complete tested unit. There is no retrofit process to convert a non-fire-rated door, frame, or hardware set into a fire-rated assembly. The entire opening must be replaced.

How much does it cost to replace a non-fire-rated assembly with a fire-rated one?

Replacement costs include the new fire-rated assembly, removal of the existing assembly, possible wall repairs, new installation labor, and potential project delays. The total cost is typically several times the price difference between fire-rated and non-fire-rated assemblies at the time of original order.

What is the difference between nominal and actual door dimensions?

Nominal dimensions are the standard size references used to describe a door (e.g., 3-0 x 7-0 for a 3-foot by 7-foot door). Actual dimensions are slightly different and account for clearances. A nominal 3-0 x 7-0 door is actually 35-3/4 inches wide. The rough opening must be sized to accommodate the actual dimensions plus the frame and installation clearances.

How do I measure a rough opening correctly?

Measure the width at the top, middle, and bottom of the opening, and the height on both sides. Use the smallest measurement in each direction. The rough opening must accommodate the frame plus shimming space on each side. Verify that the opening is plumb, level, and square before ordering.

What is the difference between KD and welded frame rough opening requirements?

Knockdown (KD) frames are typically installed after the wall is built and require a rough opening slightly larger than the frame's outside dimensions to allow for shimming and adjustment. Welded frames are set before the wall is built and are anchored in place as the wall goes up. The rough opening requirements differ because the installation sequence is different.

What happens if the rough opening is too small?

If the rough opening is too small, the frame cannot be installed without cutting into the wall to enlarge the opening. This is particularly problematic in masonry walls where enlarging the opening requires significant effort and may affect structural elements. It also delays the project while the wall work is completed.

What happens if the rough opening is too large?

If the rough opening is too large, the gap between the frame and wall may exceed what shims and sealant can accommodate. This can result in an unstable frame, visible gaps, and on fire-rated openings, a failure to meet the clearance requirements specified in the fire listing for 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute rated assemblies.

Why do doors, frames, and hardware need to be coordinated?

Doors and frames are manufactured with factory-cut preparations (preps) to accept specific hardware. If the hardware is ordered separately without referencing the door and frame preps, the hardware may not fit. For example, a mortise lock ordered for a door that was prepped for a cylindrical lock will not install.

What happens when components are ordered from different suppliers?

When doors come from one supplier, frames from another, and hardware from a third, there is no built-in verification that the preps are coordinated. Each supplier manufactures to their own order specifications, and any mismatch between those specifications results in components that do not fit together on site.

What is a hardware schedule, and why is it important for coordination?

A hardware schedule is a document that lists every hardware item for every opening on a project, including the hardware manufacturer, model, function, and finish. When doors, frames, and hardware are all ordered against the same hardware schedule, prep coordination is maintained because the schedule defines what each component must accept.

How does ProBuilder prevent prep coordination errors?

ProBuilder configures the door, frame, and hardware as a single coordinated assembly. When you select a hardware item, ProBuilder automatically applies the correct preps to the door and frame. This eliminates the risk of mismatched preps that occurs when components are ordered separately from different sources.

Can mismatched preps be corrected in the field?

Some minor prep mismatches can be corrected in the field with additional drilling or routing, but this is not recommended on fire-rated assemblies where field modifications void the fire label. For fire-rated openings at any rating level — 20-minute, 45-minute, 60-minute, 90-minute, or 180-minute — incorrectly prepped components must be replaced, not modified.

What is the difference between a welded and a KD frame?

A welded frame is a one-piece unit with joints permanently welded at the factory. It is set in place before the wall is built, with the wall constructed around the frame. A KD (knockdown) frame ships in three pieces (two jambs and a head) and is assembled on site, installed into an existing wall opening. The two types are designed for different installation sequences.

Can a welded frame be installed in an existing opening?

In most cases, no. Welded frames are designed to be set before the wall is built. Installing a one-piece welded frame into an existing opening typically requires removing wall material above and beside the opening, which may not be practical or permitted. KD frames are designed for installation into existing openings.

Can a KD frame be used in new construction instead of a welded frame?

Yes, KD frames can be used in new construction, and they are common in steel stud and drywall partitions. However, in masonry construction, welded frames set before the wall is built provide a more rigid connection. The choice depends on the wall type, project specifications, and installation sequence.

Does frame type affect fire rating?

Both welded and KD frames can be fire-rated at 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute levels. However, the specific fire listing is different for each frame type, and the installation requirements differ. The fire listing must match the actual frame type installed.

What if a welded frame was already ordered for a KD opening?

If the welded frame has not been manufactured, it may be possible to change the order to a KD frame. If the welded frame has already been fabricated or shipped, a new KD frame will need to be ordered. The welded frame cannot be field-converted to a KD configuration.

A 161 prep is the standard door preparation for cylindrical locksets. It consists of a cross bore (the large hole through the door face for the lock body) and an edge bore (the smaller hole in the door edge for the latch). The 161 designation comes from ANSI/BHMA standards and specifies the hole diameters and locations.

An 86 prep is the standard door preparation for mortise locksets. It involves a rectangular mortise pocket cut into the edge of the door to receive the mortise lock body, plus face holes for the lock trim. The mortise pocket is significantly larger than a cylindrical bore and requires a different door edge profile.

Can a door prepped for a cylindrical lock accept a mortise lock?

No. A 161 cylindrical prep has round holes that cannot accommodate the rectangular mortise pocket required for a mortise lock. A new door with the correct 86 mortise prep would be required.

What is backset, and why does it matter?

Backset is the distance from the edge of the door to the center of the lock bore (for cylindrical locks) or the center of the knob/lever hub (for mortise locks). Standard backsets are 2-3/4 inches and 2-3/8 inches. If the new door has a different backset than the existing hardware, the hardware will not align with the prep.

How do I determine what prep an existing door has?

Examine the lock side edge of the door. A cylindrical prep shows a round hole in the edge with a corresponding round hole through the door face. A mortise prep shows a rectangular pocket in the door edge. Measure the backset from the door edge to the center of the bore or hub. Document these measurements before ordering a replacement door.

How do I determine door handing?

Stand on the outside of the door (the side from which you would push to enter or the 'key side' / 'secure side'). If the hinges are on your left, it is a left-hand door. If the hinges are on your right, it is a right-hand door. If the door swings away from you, it is standard handing. If it swings toward you, add 'reverse' to the designation.

What is the difference between left hand and left hand reverse?

A left hand (LH) door has hinges on the left when viewed from the outside and swings away from you (inswing). A left hand reverse (LHR) door has hinges on the left when viewed from the outside but swings toward you (outswing). The reverse designation indicates the swing direction is opposite of standard.

Can door handing be changed in the field?

Changing door handing requires re-prepping the door and frame for hinges and hardware on the opposite side. On fire-rated assemblies, this is not permitted because field modifications void the fire label. Even on non-fire-rated assemblies, field re-prepping is labor-intensive and may not produce a clean result. Ordering the correct handing is significantly less expensive than correction.

Does handing affect hardware selection?

Yes. Some hardware is hand-specific, meaning a left-hand version cannot be used on a right-hand door. Exit devices, closers with specific arm types, and some lever trims are examples of hardware that may be hand-specific. When handing is changed, all hand-specific hardware must also be changed.

What are the most common situations where handing is specified incorrectly?

Common handing errors include confusing left and right by standing on the wrong side of the opening, forgetting to account for reverse swing, and not updating handing when architectural plans are mirrored during design revisions. Double-checking handing at the field measurement stage prevents most of these errors.

What is the difference between US26D and US32D finishes?

US26D is satin chromium plated, applied over a base metal. US32D is satin stainless steel, which is solid stainless steel throughout. US32D is more corrosion-resistant and is the standard choice for exterior or high-moisture environments. US26D is typically used in interior dry locations where cost is a consideration.

Does hardware finish affect warranty coverage?

Yes. Most hardware manufacturers specify that warranty coverage applies only when the product is installed in the environment for which the finish is rated. Installing an interior-rated finish in an exterior or corrosive environment may void the manufacturer's warranty for that component.

Should all hardware on a single opening match finishes?

Industry standard practice is to match finishes across all visible hardware on an opening — including hinges, locksets, closers, and exit devices. Mismatched finishes are a common aesthetic complaint from building owners and can indicate a specification error during project closeout review.

What finish is recommended for coastal or high-moisture environments?

US32D (satin stainless steel) is the standard recommendation for coastal, high-moisture, or corrosive environments. For extremely corrosive conditions, some manufacturers offer specialized coatings or marine-grade finishes. Consult the hardware manufacturer's environmental guidelines for the specific application.

Can hardware finish be changed after the order is placed?

In most cases, hardware finish can be changed before the order ships, but not after. Once hardware is manufactured or shipped in a specific finish, changing it requires a new order. Some finishes have longer lead times than standard options, so changes may affect the project schedule.

How far from the coast requires stainless steel hardware?

The industry standard threshold is three miles from saltwater. Buildings within three miles of any saltwater body should use stainless steel (US32D/630) hardware on all exterior openings.

Can I mix standard and stainless steel hardware on the same door?

This is not recommended. When dissimilar metals are in direct contact, galvanic corrosion occurs, accelerating corrosion at the junction.

Are stainless steel components fire-rated?

Yes. Stainless steel hardware is available in all five fire rating levels: 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute.

Page 5 - Commercial Door Parts & Hardware Guide

Parts and Hardware

Configuration Mistake: Cylindrical vs. Mortise Lock Confusion

Jason Searcy - March 29, 2026 - 7 min read

Understanding the differences between cylindrical and mortise locks and why confusion causes rework

This guide answers: When to Use Cylindrical vs Mortise Locks and Why Confusion Causes Rework

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Cylindrical Lock Basics: The 161 'Turtle Prep'

Cylindrical locks — also known as bored locks — are the most common lock type in standard commercial applications. The lock mechanism is contained in a cylindrical body that passes through a round hole (cross bore) in the door face, with a separate round hole (edge bore) in the door edge for the latch.

We use 161 cylindrical prep doors utilizing 'Turtle Prep'. It’s called this because of its distinctive profile: a large round bore on the door face paired with a smaller round bore on the edge. This visual shorthand helps specifiers and installers quickly identify the prep type in the field or on drawings.

Cylindrical

Parts and Hardware

Configuration Mistake: Improper Anchoring System Selection

Jason Searcy - March 29, 2026 - 6 min read

How choosing the wrong anchor type affects frame stability and inspection approval

This guide answers: How Anchor System Selection Affects Frame Stability and Inspection Approval

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Anchor Types and Wall Construction

The anchor system connects the door frame to the surrounding wall. Different wall constructions require different anchor types, and selecting the wrong anchor creates a structural mismatch that compromises the entire opening.

Masonry Anchors

Masonry anchors include wire anchors (for new construction, embedded in mortar joints), T-anchors (welded to the frame and embedded in masonry), and compression anchors (for existing masonry, expanded into drilled holes). Each type is designed for a specific installation sequence and wall condition.

Drywall/Stud Wall Anchors

Drywall anchors fasten the frame to steel studs through the gypsum board.

Parts and Hardware

Configuration Mistake: Non-Fire-Rated Assemblies in Code-Required Openings

Jason Searcy - March 29, 2026 - 6 min read

Understanding the consequences of installing non-fire-rated assemblies where code requires fire protection

This guide answers: What Happens If Non-Fire-Rated Assemblies Are Installed in Code-Required Openings

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Code Requirements for Fire-Rated Openings

Building codes require fire-rated door assemblies in openings within fire-rated wall assemblies. The purpose is to maintain the fire compartmentation that limits fire and smoke spread through a building. These requirements are based on the International Building Code (IBC) and are enforced by the Authority Having Jurisdiction (AHJ) during plan review and field inspection.

Common Fire-Rated Opening Locations

Corridor walls separating corridors from adjacent spaces
Stairwell enclosure walls (typically 1-hour or 2-hour rated)
Elevator shaft enclosure walls
Mechanical and electrical room walls
Occupancy

Parts and Hardware

Configuration Mistake: Rough Opening Mismatch

Jason Searcy - March 29, 2026 - 7 min read

What happens when door and frame dimensions do not match the field opening

This guide answers: What Happens If Door and Frame Configuration Doesn't Match Rough Opening

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Measuring Rough Openings

A rough opening is the hole in the wall where the door assembly will be installed. Accurate rough opening measurements are the foundation of a correct door and frame order. Errors in measurement — or failure to measure at all — are among the most common causes of configuration mistakes.

Measure the width at three points (top, middle, bottom) and the height at both sides. Record the smallest measurement in each direction, as this represents the actual usable space. Also check that the opening is plumb (vertical sides are straight) and level (top is horizontal). Out-of-plumb or out-of-level conditions may require a different frame size or type.

Nominal vs.

Parts and Hardware

Configuration Mistake: Separate Orders Without Prep Coordination

Jason Searcy - March 29, 2026 - 6 min read

How ordering doors, frames, and hardware separately causes assembly failures

This guide answers: How Separate Orders Without Prep Coordination Cause Assembly Failures

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Why Component Coordination Matters

A commercial door assembly is not a collection of independent parts — it is an integrated system where each component is manufactured to accept the others. The door is prepped with specific cutouts for the lock, hinges, and dead bolt, in addition to other possible preps like door viewers. The frame is prepped with corresponding cutouts for strike plates, hinge reinforcements, and closer brackets. The hardware is manufactured to fit those specific preps.

When all three components are ordered together against a single specification, the manufacturer coordinates the preps automatically. When components are ordered separately — especially from different

Parts and Hardware

Configuration Mistake: Welded Frames Ordered for Knockdown Openings

Jason Searcy - March 29, 2026 - 7 min read

Understanding the differences between welded and KD frames and why the wrong frame type will not fit

This guide answers: What Happens If Welded Frames Are Ordered for Knockdown Rough Openings

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Welded vs. KD Frame Construction

Welded frames are manufactured as one-piece units with joints permanently welded at the factory. The completed frame arrives on site as a single rigid assembly that maintains its square and plumb during handling and installation. Welded frames provide maximum rigidity and are the standard choice for masonry wall construction.

KD (knockdown) frames ship in three separate pieces — two jambs and one head section. These pieces are assembled on site by the installer, typically using clips, screws, or snap-fit connections at the joints. KD frames are designed to be installed into existing wall openings without requiring wall demolition.

Parts and Hardware

Configuration Mistake: Wrong Door Design for Existing Hardware

Jason Searcy - March 29, 2026 - 6 min read

How door prep selection affects compatibility with existing hardware installations

This guide answers: How Door Design Selection Affects Existing Hardware Compatibility

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Door Prep Types and Hardware Compatibility

When replacing a door in an existing frame with existing hardware, the new door must be prepared (prepped) to accept that specific hardware. Door preps are factory-cut openings in the door for locks, hinges, and other hardware. If the new door's prep does not match the existing hardware, the hardware cannot be installed.

The two most common lock preps are the 161 prep for cylindrical locksets and the 86 prep for mortise locksets. These are fundamentally different preparations that are not interchangeable.

161 Cylindrical Prep vs. 86 Mortise Prep

161 Cylindrical Prep

The 161 prep consists of a round cross bore through the door face (typically

Parts and Hardware

Configuration Mistake: Incorrect Door Handing Specification

Jason Searcy - March 29, 2026 - 6 min read

How to determine door handing correctly and what happens when it is specified wrong

This guide answers: What Happens If Door Handing Is Specified Incorrectly

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Understanding Door Handing

Door handing describes which side the hinges are on and which direction the door swings. It is one of the most fundamental specifications for a door assembly and affects the door, frame, and all hand-specific hardware. Despite its importance, handing errors are surprisingly common because the determination method can be confusing.

There are four handing designations: Left Hand (LH), Right Hand (RH), Left Hand Reverse (LHR), and Right Hand Reverse (RHR). The difference between standard and reverse is the swing direction relative to the viewer standing on the outside of the door.

How to Determine Door Handing

CDF's General Product Knowledge training provides a straightforward

Parts and Hardware

Configuration Mistake: Wrong Hardware Finish Selection

Jason Searcy - March 29, 2026 - 6 min read

How hardware finish choices affect durability, aesthetics, and warranty coverage

This guide answers: How Hardware Finish Selection Affects Durability and Warranty Coverage

Review Status

NEEDS CDF REVIEW — Created from public industry knowledge. CDF SME validation recommended to add company-specific examples and data.

Understanding Hardware Finish Designations

Hardware finishes in the commercial door industry are designated by BHMA (Builders Hardware Manufacturers Association) codes. These codes specify the base material, plating or coating, and appearance of the finished product. Common designations include US26D (satin chromium plated), US32D (satin stainless steel), US10B (oil-rubbed bronze), and US3 (polished brass).

The finish designation is more than aesthetic. Different finishes provide different levels of corrosion resistance, wear resistance, and environmental suitability. Selecting a finish based solely on appearance without considering the installation environment is a common

Parts and Hardware

Corrosion-Resistant Hardware Configuration by Environment

Jason Searcy - March 29, 2026 - 9 min read

Selecting the right materials and finishes for coastal, industrial, pool, and exterior door applications

This guide answers: When to Use Stainless Steel vs Standard Hardware in Corrosive Environments

Why Environment Matters for Hardware Selection

Standard commercial door hardware is manufactured from steel or iron with plated or coated finishes. In climate-controlled interior environments, these finishes provide decades of reliable service. In corrosive environments, however, standard hardware can begin deteriorating within months of installation.

Corrosion compromises both the function and the appearance of hardware. Hinges that corrode may bind or seize, affecting door operation and potentially creating life safety issues on egress doors. Locksets and exit devices with corroded internals may fail to latch or unlatch reliably. Beyond function, visible rust and finish deterioration on hardware undermine the appearance of the building entrance.

Selecting the correct material and finish at

Page 5 - Parts and Hardware

Review Status

Cylindrical Lock Basics: The 161 'Turtle Prep'

Review Status

Anchor Types and Wall Construction

Masonry Anchors

Drywall/Stud Wall Anchors

Review Status

Code Requirements for Fire-Rated Openings

Common Fire-Rated Opening Locations

Review Status

Measuring Rough Openings

Nominal vs.

Review Status

Why Component Coordination Matters

Review Status

Welded vs. KD Frame Construction

Review Status

Door Prep Types and Hardware Compatibility

161 Cylindrical Prep vs. 86 Mortise Prep

161 Cylindrical Prep

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Understanding Door Handing

How to Determine Door Handing

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Understanding Hardware Finish Designations

Why Environment Matters for Hardware Selection