Lock Identification Guide
Look at three things and you will usually have your answer: what is mounted on the inside face of the door, how the lock is fixed into the door, and what the keyhole sits in. A metal box screwed onto the inside surface is a rim lock. A long flat faceplate running down the edge of the door is a mortise lock. Two round holes bored through the door is a cylindrical lockset or a tubular deadbolt.
That sounds like trivia until you need something done. Whether your keys can be changed in ten minutes or the whole lock has to come out, whether that smart lock you have been looking at will physically fit, whether your co-op board has to approve anything, whether a part is sitting on a van in Brooklyn tonight or has to be ordered: all of it starts with what kind of lock is already on the door. Here is how to work it out in about a minute, standing at your own door, with nothing but your eyes.
When someone calls about a lock, the type is what we are listening for, long before brand or color. It decides four practical things.
Stand inside your apartment with the door closed and work through these five checks in order. Most doors are identified by the second one.
The signature New York apartment lock. A metal case is screwed onto the inside surface of the door, and the bolt carries two interlocking loops that drop down over a bracket mounted on the frame. Because the loops interlock rather than just sliding into a hole, the door is very hard to separate from the frame at the seam, which is exactly the attack these were designed against. From the outside you see only a cylinder. We cover the family in detail in our guide to jimmy-proof and police locks in NYC.
The lock body sits inside a rectangular pocket, the mortise, cut into the thickness of the door. The giveaway is the long faceplate on the door edge with the latch and the deadbolt both coming through it. Mortise locks are common on prewar apartment doors, brownstone entrances and commercial storefronts, and they are a genuinely good piece of hardware: heavy, repairable and long-lived. They are also the type most likely to need a specific part rather than a generic one. See mortise lock repair in NYC.
One large round hole through the face of the door and a smaller hole through the edge for the latch. The keyway is in the middle of the knob or the lever itself. These are everywhere on interior doors, office doors and secondary entrances. They are quick to work on and quick to replace, and on their own they are not a serious entry door lock.
Same two-hole preparation as a cylindrical lockset, but it is a separate lock with no handle: cylinder outside, thumbturn inside, a solid bolt that throws sideways into the frame. This is the single most common deadbolt in the country, which is why it is also the pattern nearly every consumer smart lock is built to replace.
A deadbolt and a latching handle joined by a vertical trim, so turning the inside lever retracts both at once. You will see these on apartment doors where a single motion to exit matters. From the inside they look like one tall assembly rather than two separate locks.
Lifting the outside handle throws several bolts at once along the height of the door, usually into the frame at the top, middle and bottom. Standard on modern balcony and terrace doors, newer entry doors and a lot of recent construction. Open the door and you will see the extra bolts spaced down the edge. These have their own failure modes, covered in multi-point lock repair in NYC.
Less common than it used to be, still out there in older buildings. A steel bar braces from the lock into a socket set in the floor, so pressure on the door is transferred to the floor instead of the frame. Unmistakable once you have seen one, and genuinely strong. It is also the heaviest thing on this list to operate every day.
Keypad, fob or app, usually built on top of one of the mechanical formats above. The important question with these is not the electronics but what is underneath, because that is what determines whether it could be installed in the first place and what happens when the batteries die. Our guide to keyless entry for a NYC apartment covers the practical side.
| Lock type | How to spot it | Where it turns up in NYC |
|---|---|---|
| Rim / jimmy-proof | Metal case on the inside face, bolt loops drop onto a frame bracket | Apartment entry doors, often as the second lock |
| Mortise | Long faceplate on the door edge, latch and bolt together | Prewar buildings, brownstones, storefronts |
| Cylindrical lockset | Key in the knob or lever, one big hole through the face | Interior doors, offices, secondary doors |
| Tubular deadbolt | Separate lock, no handle, cylinder outside and thumbturn inside | Houses, newer apartment doors, additions |
| Interconnected | Deadbolt and lever joined by a vertical trim | Apartment doors where one motion must open everything |
| Multi-point | Several bolts down the door edge, handle lifts to lock | Terrace and balcony doors, newer construction |
| Bar lock | Steel bar braced into a floor socket | Older walk-ups and ground-floor units |
This is where most people get tangled. The lock type tells you how the hardware is mounted in the door. The cylinder is the keyed plug that sits inside it, and it is usually a separate, replaceable part with its own format.
Why this matters: changing which key opens a door is almost always work on the cylinder, not on the lock body. That is the whole idea behind rekeying, and it is why the honest answer to most lock-change requests is cheaper than people expect. When the cylinder itself is worn, damaged or the wrong grade, swapping it is still a smaller job than replacing the lock, as our guide to lock cylinder replacement explains.
You do not need the right vocabulary. You need the right observations. Give a locksmith these and the conversation gets specific fast.
Once the type is settled, the practical decisions fall out of it. If you only want new keys, you are looking at a rekey of the cylinder regardless of which family your lock belongs to, and our comparison of rekeying versus replacing a lock covers when that stops being the right call.
If you want to upgrade, the type sets the menu. A tubular deadbolt gives you the widest choice, including most keypad and smart locks. A mortise lock is usually best improved by upgrading its cylinder rather than ripping out a good lock body. A rim lock can often take a better cylinder too, and it is worth keeping rather than removing, because it does something the other types do not. If you are weighing a genuine upgrade, read which lock type suits a NYC apartment and our explanation of ANSI lock grades so you are comparing on something real rather than on packaging.
And if the reason you are identifying the lock is that it has become stiff or awkward to operate, the type may be beside the point. Hardware that is hard to work is frequently a door alignment problem wearing a lock costume, which is the first thing worth ruling out. Our guide to easy-to-use door locks for seniors goes through that in detail, and it applies to anyone whose door has started to fight back.
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Look at the edge of the door and at the inside face. A mortise lock sits inside a pocket cut into the thickness of the door, so the only thing visible on the edge is a long flat faceplate with the latch and the bolt coming through it. A rim lock is screwed onto the inside surface of the door as a visible metal case, and its bolt drops vertically onto a bracket on the frame.
That is a rim lock, usually called a jimmy-proof or vertical deadbolt. The two interlocking loops on the bolt drop over a bracket mounted on the door frame, which is what makes the door very hard to pry open at the seam. It is the most common second lock on older New York City apartment doors.
Not by itself. The name stamped on the key bow tells you who made the cylinder, which is a different question from how the lock body is mounted in the door. The same manufacturer sells rim cylinders, mortise cylinders and key-in-knob cylinders, so you still have to look at the door to know what you have.
No. Most consumer smart locks are built to replace a standard tubular deadbolt that sits in two round bored holes. If your door has a mortise lock, a rim lock or a multi-point system, a direct swap is usually not possible without changing the hardware or the door preparation, and in a co-op or rental some of those changes need building approval first.
Usually not. On most lock types the keyed cylinder is a separate part, so changing which key operates the door is a rekey of that cylinder rather than a new lock. Replacement is the better answer when the lock body is worn or damaged, or when you want a different grade or function than the one you have.
Take four photos: the inside face of the door showing the whole lock, the edge of the door with the door open so the faceplate and bolt are visible, the outside of the door around the keyhole, and the key laid flat on a plain surface. Those four images answer almost every identification question without a visit.