Here's a plain-language breakdown so you can pick the right one without overthinking it.

What Is a Mortise Lock

A mortise lock lives inside the door. To install one, a rectangular pocket (the mortise) has to be cut into the door edge. The lock body, which is a self-contained steel case, drops into that pocket and houses the latch bolt, deadbolt, and internal mechanism all in one unit. The lever or knob trim attaches through the door face with through-bolts that run the full thickness of the door.

That deep, integrated installation is what makes mortise locks strong. The mechanism is anchored inside the door structure itself, not just surface-mounted. The result is a lock that resists forced entry, handles heavy daily use, and offers more function options like entry, classroom, storeroom, and office functions, all within the same lock body.

You'll find mortise locks on the primary entrances of hotels, office buildings, schools, and government facilities. Any commercial door that sees constant traffic and needs serious security is a candidate for a mortise lock.

What Is a Cylindrical Lock

A cylindrical lock installs through two round bored holes drilled into the door: a larger hole through the face and a smaller one through the edge for the latch. The lock chassis sits in the face bore, and the latch mechanism sits in the edge bore. Lever or knob trim threads onto each side.

It's a simpler system. Installation is faster, the hardware costs less, and most doors in commercial buildings already come pre-drilled for cylindrical preps. That's why cylindrical locks are the most common lock type overall. They're practical, widely available, and perfectly adequate for a huge range of applications.

Most interior commercial doors use cylindrical locksets: office rooms, storage closets, conference rooms, restroom corridors. Grade 1 cylindrical locks from brands like Schlage, Sargent, or Yale handle this kind of use comfortably for years.

The Key Differences Side by Side

Installation

Cylindrical locks install in minutes on a pre-drilled door. Mortise locks require a precisely cut pocket in the door edge, and it's a more involved process and typically needs to be done by a professional or specified at the time the door is manufactured. Once the door prep exists, swapping hardware is straightforward. But you can't put a mortise lock on a door drilled for cylindrical hardware, or vice versa. The two preps are incompatible with no field workaround.

Security and Strength

Both types come in ANSI/BHMA Grade 1, which is the commercial standard. But a Grade 1 mortise lock and a Grade 1 cylindrical lock aren't structurally identical. The mortise lock's integrated case gives it an inherently stronger platform. The latch, bolt, and springs all live in one reinforced unit anchored deep in the door. A cylindrical lock relies more on the door's structural integrity around the bore holes. For primary entries and high-security applications, mortise wins. For standard interior commercial doors, a Grade 1 cylindrical lock is more than sufficient.

Functions Available

Mortise locks offer a wider range of functions in one unit, including entry, classroom, storeroom, hotel, and apartment functions, without needing separate hardware. Cylindrical locks also cover these functions but sometimes require adding a separate deadbolt to match the security level of a mortise set. Mortise locks also offer significantly more trim design options, which matters in architectural or high-end commercial projects where appearance is part of the specification.

Cost

Cylindrical locks are less expensive. Good Grade 1 commercial cylindrical hardware runs roughly $150 to $350 per opening. Grade 1 mortise locksets start around $300 and can go well past $600 per opening, not including professional installation labor for new door prep. On a building with 150 doors, that cost difference is significant. The right answer is using mortise where it's genuinely needed and cylindrical everywhere else, not defaulting to one type for the whole project.

Long-Term Durability

In heavy-use commercial environments, mortise locks tend to last longer. Their integrated design distributes stress across a larger case, which holds up better under constant door cycling. Cylindrical locks work well in their right applications but can wear out faster on a primary entry that processes hundreds of people a day. Mortise locks hold about 40% of the commercial door hardware market, favored for their durability in demanding environments, while cylindrical locks account for the remaining 60%, chosen for cost-effectiveness and straightforward installation.

Which One Should You Choose

The honest answer is: it depends on what the door is doing.

Use a mortise lock when: the door is a primary exterior entry, a high-traffic corridor in a school or healthcare facility, a hotel room entry, or any opening where security and long-term durability are the top priorities. Also use mortise when the door is already prepped for it. There's no reason to modify a door that's built for mortise hardware.

Use a cylindrical lock when: the door is an interior office, storage room, conference room, or any lower-traffic opening where a Grade 1 cylindrical lockset covers the security requirement. Most interior commercial doors fall into this category. Cylindrical is also the practical choice when budget is a real constraint on a multi-door project.

Never mix preps on the same door. If a door was manufactured with a cylindrical prep (ANSI 161), it needs cylindrical hardware. If it has a mortise prep (ANSI 86), it needs a mortise lock. Ordering the wrong one means returning it and waiting for the right hardware, a mistake that's easy to avoid by confirming the door prep before you order.

What About ANSI Grades

For any commercial door, Grade 1 is the right starting point. Both mortise and cylindrical locks are available in Grade 1 under ANSI/BHMA standards. A156.13 covers mortise locks and A156.2 covers cylindrical locks. Grade 1 cylindrical locks are tested to 800,000 cycles. Grade 1 mortise locks are held to similar cycle requirements with additional strength testing for the bolt and case.

Grade 2 is acceptable for interior commercial doors with light use. Grade 3 is residential hardware and shouldn't appear on a commercial specification. If you see a lock listed without a grade, skip it. The absence of certification is a red flag regardless of what the marketing says.

Top Brands to Know

For mortise locks, the names you'll see on most commercial specifications are Schlage (L-Series), Sargent (7000 Series), Corbin Russwin (ML2000 Series), and Yale (8800 Series). These are the brands architects and facility managers specify by name on door hardware schedules.

For cylindrical locks, Schlage (AL and ND Series), Sargent (10 Line), Best (9K Series), and Cal-Royal are the dominant commercial options. All manufacture Grade 1 products with interchangeable core options for large facilities that need master key systems.

Shop Door Locks at SecurityParts.com

SecurityParts.com carries both mortise and cylindrical locksets from the brands contractors and facility managers rely on. Every product listing includes the manufacturer's spec sheet so you can confirm the ANSI grade, function, and door prep before ordering.

Whether you're sourcing hardware for a full door schedule or replacing a single lockset, browse our mortise locks and cylindrical locks to find the right fit for your opening.

Frequently Asked Questions

What is the difference between a mortise lock and a cylindrical lock?

A mortise lock installs inside a rectangular pocket in the door edge and houses the latch, deadbolt, and mechanism in one steel case. A cylindrical lock installs through two round bored holes in the door and is a simpler, more compact system. Mortise locks are stronger and offer more functions. Cylindrical locks are faster to install and more affordable.

Which is better for commercial doors: mortise or cylindrical?

Mortise locks are the standard for primary commercial entries and high-traffic openings. Cylindrical locks are widely used on interior commercial doors like offices and storage rooms where security demands are more moderate. Both are correct answers, just for different doors.

Can I replace a mortise lock with a cylindrical lock?

No. The door preps are incompatible. A mortise lock needs a rectangular pocket in the door edge. A cylindrical lock needs two round bored holes. There's no field modification that bridges them. You need hardware that matches the prep the door was built with.

How much does a commercial mortise lock cost compared to a cylindrical lock?

Grade 1 cylindrical hardware typically runs $150 to $350 per opening. Grade 1 mortise locksets generally start around $300 and can exceed $600, not including professional labor for new mortise prep work. Cylindrical costs less upfront. Mortise tends to offer better long-term value on heavy-use commercial doors.

What ANSI grade should a commercial door lock be?

Grade 1 for exterior, high-traffic, and fire-rated commercial doors. Grade 2 is acceptable for low-traffic interior doors. Grade 3 is residential only and shouldn't appear on any commercial specification.