Choosing between a mortise lock and a cylindrical lock isn't just a hardware preference, it's a decision that affects how secure a door is, how much it costs to install and service, and whether it will hold up to the traffic a specific opening sees every day. Architects and facility managers run into this choice constantly when specifying or replacing hardware, and picking the wrong one can mean a door that's either over-built for a closet or under-built for a building entrance. This guide breaks down what separates a mortise lock from a cylindrical lock, where each one belongs, and how to decide which is right for your project.
A mortise lock is a lock body that sits inside a pocket, or “mortise,” cut into the edge of the door itself. The lock case houses the latch, deadbolt, and often additional functions like an auxiliary latch, all in a single rectangular unit. Because the mechanism is recessed into the door rather than mounted through it, mortise locks are typically built with heavier-gauge steel components and more internal parts than a cylinder lock, which is part of why they tend to be ANSI Grade 1, the highest commercial duty rating.
Mortise locks are common on doors that take heavy daily use or need a higher level of security: main entrances, stairwells, hotel guest room doors, and high-traffic commercial doors where hardware failure isn't an option.
A cylindrical lock is a lock where the locking mechanism is housed in two separate cylindrical units, one on each side of the door, connected through a hole bored straight through the door face. Unlike a mortise lock, there's no pocket cut into the door edge, just two cross-bores: one through the face of the door and one through the edge for the latch.
Cylindrical locks are available in both Grade 1 and Grade 2 ratings, which makes them more flexible across a wider range of applications, from office suites and classrooms to storage rooms and restrooms.
A mortise lock requires a precisely cut pocket in the door edge, which means more labor during installation and during any future hardware change-out (a different mortise lock body usually requires the same prep). A cylindrical lock installs through two bored holes, which is faster to install and easier to swap on a retrofit since most cylindrical locks share a standard bore pattern.
Mortise locks generally outperform cylindrical locks on raw durability because the lock case is fully enclosed in steel and the components are more substantial. Most mortise locks are ANSI Grade 1, built for the highest cycle counts and resistance to forced entry. Cylindrical locks span Grade 1 and Grade 2, so the durability gap depends on which grade you're comparing. A Grade 1 cylindrical lock can hold up well in moderate-to-high traffic settings, while Grade 2 is suited to lighter-duty interior doors.
If you're unsure which ANSI grade fits your application, our guide to ANSI Grade 1 vs. Grade 2 door hardware breaks down the cycle testing and use cases behind each rating.
Mortise locks typically offer more built-in function options within a single lock body, things like deadbolt and latch combinations, or trim variations for entry, classroom, or storeroom functions, without changing the core mechanism. Cylindrical locks offer function variety too, but each function is usually a separate lock rather than a configuration of one body.
Cylindrical locks cost less to purchase and install in most cases, since the bore-through installation requires less door prep and labor. Mortise locks cost more upfront, but that cost reflects the added durability and the labor savings over the life of the door, since a well-specified mortise lock generally needs less frequent replacement.
Mortise locks tend to have a more refined trim profile since the lock case is hidden inside the door, which is one reason they're common in hospitality and upscale commercial settings where aesthetics matter alongside security.
There's no universal right answer between the two. Many commercial buildings use both, mortise locks on main entrances and high-security or high-traffic doors, cylindrical locks throughout the rest of the building where the cost and installation speed make more sense.
Mortise locks and cylindrical locks both do the same basic job, but they get there differently, and that difference matters once you factor in traffic, security needs, and budget across a real project. A mortise lock earns its higher price tag on doors that need to perform at the highest duty cycle for years without failure. A cylindrical lock earns its place everywhere else, where speed of installation and lower cost per opening matter more than maximum strength. Most commercial buildings end up using both, and that's the right call, not a compromise.
If you're specifying hardware for an upcoming project, the door's traffic level and security requirement should drive the decision more than habit or what was used last time.
Generally yes, when comparing a mortise lock to a Grade 2 cylindrical lock. Mortise locks are typically ANSI Grade 1 and built with heavier internal components. When compared to a Grade 1 cylindrical lock, the security gap narrows, since both meet the same high-duty cycle and strength standards.
Not as a simple swap. Because a mortise lock requires a pocket cut into the door edge and a cylindrical lock uses bored-through holes, converting from one to the other usually requires new door prep or a new door entirely.
Cylindrical locks are typically cheaper to install because the bore-through preparation takes less labor than cutting a mortise pocket. Mortise locks cost more upfront but can offer lower lifetime cost on high-traffic doors due to their durability.
Both can be integrated into the same keying system or master key plan, including PDQ's VAULT patented keying platform. The lock body type doesn't restrict which keying system you can use.
Most commercial entrances call for ANSI Grade 1 hardware, whether that's a mortise lock or a Grade 1 cylindrical lock, due to the cycle count and security demands of a primary entry point.
Choosing between a mortise lock and a cylindrical lock often comes down to the specifics of your project: door traffic, security requirements, budget, and the building type. If you're working through a spec and want a second opinion, talk to a PDQ expert about which lock body fits your application.
Looking for the technical cut sheets and specification details to drop into your spec? Our Price Book and Product Digest cover the full range of PDQ mortise and cylindrical lock options, grades, and functions.