Mortise locks and cylindrical locks are two of the most common lock types used on commercial doors. From the outside, they can look surprisingly similar. Both may use lever handles, keyed cylinders, classroom functions, storeroom functions, passage functions, or electronic access options.
Behind the trim, however, they are built very differently.
A mortise lock uses a comparatively large lock case installed inside a rectangular pocket cut into the edge of the door. A cylindrical lock uses a compact chassis installed through bored openings in the faces and edge of the door.
The correct choice depends on the door preparation, required function, traffic level, security requirements, keying system, project specifications, and whether you are working with a new door or replacing existing hardware.
This guide explains the differences so you can choose the right commercial lock without unnecessarily modifying the door.
Mortise Lock vs. Cylindrical Lock: Quick Answer
The most important difference between mortise and cylindrical locks is how they fit into the door.
- Mortise locks fit inside a rectangular pocket, or mortise, cut into the door edge.
- Cylindrical locks fit through bored holes in the door and use a separate latch installed through the door edge.
Mortise locks are frequently selected for demanding commercial and institutional openings because their larger lock cases can support a wide range of functions and configurations.
Cylindrical locks are widely used throughout commercial buildings because they can provide strong commercial performance with a simpler bored-door preparation.
Neither type should be selected by appearance alone. The exact lock grade, function, door preparation, cylinder format, listing, and manufacturer specifications matter more than the general lock category.
What Is a Mortise Lock?
A mortise lock is installed inside a rectangular cavity cut into the edge of the door. The lock body sits almost entirely inside this pocket, while the lever, knob, rose, escutcheon, cylinder, thumbturn, and other trim are mounted to the faces of the door.
Depending on the model and function, the mortise lock body can contain:
- Latchbolt
- Deadbolt
- Locking mechanism
- Lever or knob hubs
- Cylinder interface
- Thumbturn mechanism
- Electrical switches or solenoids on electrified models
This construction gives manufacturers room to offer a wide variety of commercial locking functions and trim configurations.
Browse our Mortise Locks or Commercial Mortise Locks when working with a mortise-prepped opening.
What Is a Cylindrical Lock?
A cylindrical lock uses a compact chassis that passes through a bored opening in the door. A latch assembly extends separately from the chassis through the door edge and engages the strike in the frame.
The exterior and interior levers or knobs connect through the lock chassis.
This design is commonly found on:
- Office doors
- Classrooms
- Storerooms
- Service rooms
- Retail spaces
- Multifamily common areas
- Interior commercial doors
- Other bored-door commercial openings
Cylindrical locksets are available in multiple commercial grades and functions. Heavy-duty Grade 1 cylindrical locks are widely used in commercial and institutional buildings, so cylindrical construction should not be confused with residential-duty hardware.
See our Commercial Entry Door Levers for examples of commercial cylindrical lock configurations.
The Biggest Difference Is Door Preparation
If you are replacing existing hardware, door preparation is usually the first thing you should identify.
A mortise-prepped door has a large rectangular pocket cut into the door edge to accept the lock case.
A cylindrical-prepped door typically has a round bore through the faces of the door along with a smaller edge bore for the latch.
These preparations are substantially different.
A mortise lock normally cannot be installed into a standard cylindrical preparation without major modification to the door. Likewise, replacing a mortise lock with a cylindrical lock can leave an oversized mortise pocket and unused trim preparations that must be properly addressed.
For replacement projects, staying with the existing lock format is generally the simplest approach unless the door is intentionally being modified or replaced.
Which Is Stronger: Mortise or Cylindrical?
Mortise locks are commonly associated with heavy-duty applications because the larger internal lock case allows substantial mechanical components and a broad range of functions.
However, you should not assume that every mortise lock is automatically stronger than every cylindrical lock.
Commercial cylindrical locks are available in very robust Grade 1 configurations designed for high-use doors.
The better comparison is therefore:
What is the grade and intended application of the specific lock?
Look at the manufacturer's specifications for cycle testing, security grade, latch construction, lever strength, listings, intended application, and other performance requirements rather than deciding based only on whether the lock is mortise or cylindrical.
Grade 1 vs. Grade 2 Commercial Locks
Commercial locksets may be classified by ANSI/BHMA performance grades.
Grade should be evaluated separately from lock construction.
You can find:
- Grade 1 mortise locks
- Grade 1 cylindrical locks
- Grade 2 cylindrical locks
- Other products intended for different levels of use
A Grade 1 cylindrical lock may therefore be more appropriate for a demanding commercial opening than a lower-duty product simply because that other product uses mortise construction.
Always verify the grade of the exact model being ordered.
Mortise and Cylindrical Lock Functions
Both mortise and cylindrical lock families can be offered in numerous operating functions.
Common commercial functions include:
Passage
Both sides remain unlocked and operate the latch. Passage locks are commonly used where no locking function is required.
Entry or Office
The outside lever can be locked while the inside lever normally allows egress. Exact locking and unlocking operation varies by manufacturer and function designation.
Classroom
Classroom functions are generally designed so authorized personnel can control the outside lever with a key while maintaining free egress from the inside.
Storeroom
Storeroom locks typically keep the outside lever locked while the inside lever remains available for egress. The key normally retracts the latch from outside but does not leave the exterior lever permanently unlocked.
Privacy
Privacy locks are used on restrooms, dressing rooms, patient rooms, and other openings requiring occupant privacy rather than conventional keyed security.
Function names can sound similar between brands while operating differently. Always review the manufacturer's exact function description before ordering.
Which Is Easier to Install?
For a new door that has not yet been prepared, cylindrical locks generally require a simpler door preparation than full-size mortise locks.
A cylindrical lock commonly requires a cross bore through the door, an edge bore for the latch, and the correct strike preparation in the frame.
A mortise lock requires a precisely sized pocket in the door edge plus the necessary trim, cylinder, spindle, through-bolt, and faceplate preparations for the particular lock.
That does not mean mortise locks are unusually difficult for a properly prepared commercial door. Commercial hollow metal and wood doors can be factory-prepared specifically for the intended hardware.
The difficulty usually arises when someone tries to install a lock into a door prepared for a different lock type.
Replacing an Existing Commercial Lock
Replacement work should begin with identification, not with finish or lever style.
If possible, find the manufacturer and series number before removing anything.
Check:
- Manufacturer
- Series
- Lock function
- Door preparation
- Backset
- Door thickness
- Latch or lock-case dimensions
- Faceplate dimensions
- Strike preparation
- Lever or knob trim
- Rose or escutcheon preparation
- Handing when applicable
- Cylinder or interchangeable-core format
- Keyway
- Existing fire or other listing requirements
With mortise hardware, the exact lock body is especially important. Two mortise lock cases can appear similar and still have different dimensions, hub positions, cylinder locations, functions, or trim preparations.
Our Mortise Lock Bodies collection includes complete lock bodies and replacement components for mortise-prepped doors.
Backset Matters on Both Lock Types
Backset is the distance from the door edge to the centerline of the primary lock preparation.
Commercial locks commonly use standardized backsets, but options vary between lock families.
Do not assume the backset based on the age of the building or appearance of the hardware.
Measure the existing preparation or identify the current model before ordering.
For measurement instructions, see our guide explaining how to measure door backset.
Door Thickness Is Also Important
Both mortise and cylindrical locks are designed around specified door-thickness ranges.
Commercial doors are often 1-3/4 inches thick, but that does not mean every commercial lock automatically fits every 1-3/4-inch door.
Thicker doors, thin doors, lead-lined doors, specialty openings, and custom trim installations can require additional parts or a specific factory configuration.
Always verify the door thickness range for the exact lock.
Mortise Locks and Handing
Handing can matter more with certain mortise lock configurations than with many standard cylindrical locks.
Some mortise products are field reversible, while others must be ordered or configured for a specific handing, bevel, function, or trim arrangement.
Do not assume that a replacement lock body can simply be flipped around.
If the manufacturer's model number includes handing information, match it carefully before ordering.
What About Cylinders and Keying?
The words mortise and cylindrical describe the lock construction, not necessarily the keying system.
Commercial lock families can support different cylinder formats, including:
- Conventional keyed cylinders
- Full-size interchangeable cores
- Small-format interchangeable cores
- Less-cylinder configurations
- Less-core configurations
- Restricted or patented key systems
If a new lock must operate within an existing facility master-key system, determine the required cylinder and keyway before selecting the lock.
A lock that fits perfectly in the door can still be the wrong product if its cylinder is incompatible with the building's key system.
Are Mortise Locks Better for Master Key Systems?
Both mortise and cylindrical commercial lock families can support sophisticated keying systems.
Master key capability is determined by the cylinder or interchangeable-core system used by the lock, not simply by whether the lock chassis is mortise or cylindrical.
When matching an existing key system, verify the manufacturer, cylinder format, keyway, core type, and keying requirements.
What About Electronic Locks?
Electronic access control does not eliminate the distinction between mortise and cylindrical construction.
Electronic locks may be built around:
- Cylindrical lock chassis
- Mortise lock chassis
- Exit-device trim
- Other access-control hardware formats
Before selecting electronic hardware, identify the existing door preparation first. Then confirm credential type, power requirements, cylinder override, lock function, fire listing, access-control compatibility, and any monitoring requirements.
Mortise Locks on Fire-Rated Doors
Do not assume that a mortise lock is approved for a fire-rated door simply because mortise locks are commonly used in commercial buildings.
The exact lock must have the appropriate listing for the opening and must be installed according to the manufacturer's instructions and the requirements of the complete fire-door assembly.
The same principle applies to cylindrical locks.
Fire-door suitability is determined by the tested and listed product and assembly, not merely by lock type.
Are Cylindrical Locks Allowed on Commercial Doors?
Yes. Cylindrical locks are widely used on commercial doors.
They are available in multiple functions, grades, lever styles, cylinder formats, and listed configurations.
The appropriate product depends on the requirements of the opening.
Browse Commercial Door Hardware to compare locksets and related components used throughout commercial buildings.
When Does a Mortise Lock Make Sense?
A mortise lock may be an especially good choice when:
- The door is already mortise-prepped
- The project hardware specification calls for mortise locks
- A specific mortise function is required
- The building uses an existing mortise lock family
- Architectural trim must coordinate with an established system
- The opening requires features offered by the selected mortise platform
- Replacement compatibility favors retaining the existing mortise preparation
When Does a Cylindrical Lock Make Sense?
A cylindrical lock may be an especially good choice when:
- The door already has cylindrical preparation
- A straightforward commercial bored-lock installation is desired
- The required function is available in the chosen cylindrical series
- A suitable Grade 1 or Grade 2 product meets the application requirements
- The project specification calls for cylindrical locks
- Maintaining an existing cylindrical lock family simplifies maintenance and keying
New Construction vs. Replacement Projects
New Construction
On a new project, the architect, contractor, hardware consultant, door supplier, or facility team can coordinate the door preparation with the selected lock before the doors are manufactured.
This provides more flexibility when choosing between mortise and cylindrical hardware.
Replacement Projects
On an existing door, the preparation has already been established.
Changing lock formats can require extensive modification to the door, reinforcement, edge preparation, trim holes, and frame strike.
For this reason, the existing preparation should heavily influence the replacement decision.
How Can You Tell Which Lock You Have?
You can often identify the lock type by examining the door edge.
A mortise lock typically has a relatively tall faceplate because a larger lock case sits inside the door.
A cylindrical lock usually has a much smaller latch faceplate on the door edge, while the primary chassis is positioned behind the lever or knob trim.
For a more reliable identification, look for:
- Brand name
- Series markings
- Model numbers
- Labels on the door edge
- Stamping on the latch or faceplate
- Original hardware schedule
- Installation instructions retained by the building owner
Photos of the edge of the door, both sides of the trim, and any visible markings can also help when comparing replacement hardware.
Common Mistakes When Choosing Commercial Locks
Choosing by Appearance
Two lever locks can look almost identical from the hallway while using completely different internal chassis and door preparations.
Assuming Mortise Automatically Means Grade 1
Lock construction and performance grade are separate specifications. Verify the exact manufacturer's grade.
Assuming Cylindrical Means Light Duty
Commercial Grade 1 cylindrical locks are designed for demanding applications and are widely used in institutional and commercial buildings.
Ignoring Existing Door Preparation
This is one of the most expensive mistakes. Changing from cylindrical to mortise or mortise to cylindrical can require substantial door modification.
Ordering the Wrong Function
Classroom, storeroom, office, passage, privacy, and other functions operate differently even when the trim looks the same.
Ignoring the Keying System
A lock must work with the building's required cylinder, core, and keyway if it is being integrated into an existing key system.
Assuming a Fire Rating Applies to Every Version
Listings and ratings should be confirmed on the exact product and configuration being installed.
Mortise vs. Cylindrical Lock Replacement Checklist
Before ordering a commercial lock, confirm:
- Mortise or cylindrical door preparation
- Manufacturer
- Lock series
- Required function
- ANSI/BHMA grade when applicable
- Door thickness
- Backset
- Door handing when applicable
- Latch or mortise case dimensions
- Faceplate dimensions
- Strike preparation
- Lever or knob style
- Rose or escutcheon preparation
- Cylinder or interchangeable-core format
- Keyway
- Master-key requirements
- Fire or other required listings
- Electrical requirements when applicable
- Finish
Frequently Asked Questions
Is a Mortise Lock More Secure Than a Cylindrical Lock?
Mortise locks are frequently used for heavy-duty and high-security applications, but lock type alone does not establish security performance. A high-quality Grade 1 cylindrical lock can also provide substantial commercial security. Compare the grade, construction, function, cylinder, installation, and manufacturer specifications of the actual products.
Can I Replace a Cylindrical Lock With a Mortise Lock?
Not as a simple drop-in replacement. The door normally requires substantial additional preparation to create the mortise pocket and accommodate the new trim.
Can I Replace a Mortise Lock With a Cylindrical Lock?
It is possible as part of a planned door modification, but it is generally not a direct replacement. The existing mortise pocket and trim preparations need to be properly addressed.
Are Cylindrical Locks Good for Schools?
Commercial cylindrical locksets are available in heavy-duty configurations for school and institutional applications. The exact function, grade, classroom security requirements, key system, fire listing, and project specification should determine the product.
Are Mortise Locks Only for Commercial Buildings?
No. Mortise locks are also used in residential architectural hardware, particularly on higher-end entry doors and traditional door-hardware systems.
Are Cylindrical Locks Only for Residential Doors?
No. Commercial cylindrical locks are an established category of commercial door hardware and are available in Grade 1 and Grade 2 configurations.
Which Lock Is Easier to Repair?
That depends on the lock family and which component has failed. Mortise systems often offer replaceable lock bodies and components, while commercial cylindrical locksets also have series-specific latches, chassis components, trim, and cylinders. Identify the manufacturer and series before ordering repair parts.
What Does “Less Cylinder” or “Less Core” Mean?
It generally means that the lock is supplied without the keyed cylinder or interchangeable core so the appropriate cylinder can be installed separately. This is common on commercial projects where the building uses a specific key system.
Choosing the Right Commercial Door Lock
The choice between a mortise lock and a cylindrical lock should start with the door and the required function, not the lever style or finish.
For replacement projects, identify the existing preparation before ordering. If the door already has a mortise pocket, replacing it with compatible mortise hardware is usually the most straightforward path. If the door is prepared for a cylindrical lock, staying with a compatible cylindrical platform generally avoids unnecessary modification.
For new construction, either format may be appropriate depending on the hardware specification, use of the opening, traffic level, security requirements, keying system, function, and desired lock family.
Most importantly, do not assume that mortise automatically means heavy duty or that cylindrical means residential. Commercial products are available in multiple performance grades and configurations within both categories.
Browse Factory Direct Hardware's Mortise Locks, Commercial Mortise Locks, Mortise Lock Bodies, Commercial Entry Door Levers, and Commercial Door Hardware to compare available options.
For additional terminology, visit our Hardware Glossary, or browse the Factory Direct Hardware Learning Center for more guides covering door locks, hinges, closers, measurement, and commercial hardware.
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