NYC Apartment Security
A jimmy-proof deadbolt and a police lock answer two different attacks on the same New York door. The jimmy-proof deadbolt - the surface-mounted lock whose two vertical bolts drop through a strike on the jamb - defeats prying the door away from the frame. A police lock is a steel brace running from a socket in the floor to the back of the door, so a battering force is carried into the floor instead of the frame. Most prewar apartment doors in the city carry one, the other, or both.
You will hear it called a jimmy-proof lock, a vertical deadbolt, an interlocking deadbolt, or a Segal lock after one of the long-running manufacturers. All describe the same mechanism, worth understanding because so many apartment doors in the older boroughs have one.
The lock body mounts on the inside surface of the door rather than in a pocket cut into the door edge. Two short bolts sit vertically in that body. The strike is a separate plate with two rings on it, screwed to the face of the jamb. Throw the lock and the bolts drop through those rings, interlocking door and frame in the vertical plane.
That geometry is the whole point. A conventional deadbolt throws one bolt horizontally into a hole in the jamb; lever the door edge away from the frame and the bolt can clear the hole - that is what jimmying means. Vertical bolts passing through rings do not come free when the gap widens.
On the outside is a rim cylinder, a round cylinder with a flat tailpiece passing through the door to drive the lock body, with a thumb turn inside. That cylinder is a separate, inexpensive part, which matters when you get to rekeying - and on an old lock it is usually the most worn component in the assembly.
One thing a jimmy-proof deadbolt is not is a latch. It does not hold the door shut on its own, which is why these doors almost always pair it with a spring-latch knob or a separate latch lock. For how it compares with everything else you could put on an entry door, see the best lock type for an NYC apartment.
A police lock - often called a Fox lock, after the manufacturer most New Yorkers associate with it - is a brace, not a bolt. A steel bar sits at an angle, its lower end seated in a metal socket set into the floor a foot or two back from the door, its upper end engaging a bracket on the back of the door.
Hit that door and the force does not try to break the jamb, the strike, or the screws. It runs down the bar into the floor. That is why police locks exist in a city of old doors in old frames: however good your deadbolt is, a jamb-mounted lock is limited by the wood it is screwed into, and a brace sidesteps that entirely.
Two families are common. The angled floor-brace type is set from inside, making it a lock you use when you are home, though keyed versions exist that pivot the bar from an outside cylinder. The other is the double-bar lock, where two horizontal bars slide from a central mechanism into pockets on both sides of the frame.
The trade-offs are honest. A brace needs a floor socket, which means drilling your floor - a real conversation in a co-op, condo, or rental, and sometimes a flat no. And because the better-known versions are inside-only, a police lock supplements an entry lock set rather than replacing one.
The hardware follows the building stock. Brownstones, tenements, and prewar apartment houses were built with solid wood doors in wood frames, and after decades of settling and painting, those frames are rarely square and the wood around the strike is rarely fresh. Cutting a deep mortise into a hundred-year-old door for a modern bored deadbolt is sometimes not possible without weakening it.
A surface-mounted lock asks nothing of the door edge: it screws onto the face and works on a door of almost any thickness. Combine that with a brace that ignores the frame altogether and you have a package suited to the doors the city actually has - which is why these locks keep getting reinstalled rather than retired.
Most service calls on these locks are not break-ins. They are the slow consequences of an old building moving.
If the symptom is the door rather than the lock - dragging, not closing, not staying shut - start with a door that will not lock properly, because no hardware fixes a door that is not hanging right.
We service, align, rekey, and replace vertical deadbolts, rim cylinders, and brace locks on apartment and brownstone doors across all five boroughs - including doors that have moved with the building.
If the door also carries an old mortise lock - very common on prewar apartment and brownstone doors - that is a separate unit with its own failure modes; see mortise lock repair in NYC. If only the cylinder is at fault on any of them, lock cylinder replacement is usually the cheapest path back to a working door.
Before adding or swapping hardware on an apartment entrance door in New York, three things govern what you can do, and they stack.
One safety point overrides preference: an apartment entrance door has to let people out. A lock needing a key to open from inside, or a brace nobody can release in the dark, is a problem in a fire however secure it feels - the principle behind fire escape door lock requirements. Take questions about a specific door assembly to your managing agent and a licensed professional. And if you are reading this from the hallway rather than planning an upgrade, being locked out of an NYC apartment covers the call - tell whoever you ring what is on the door, because these locks change the approach.
Against prying, they do what the name says - two vertical bolts passing through rings on the strike do not disengage when the door is levered away from the frame. The name does not cover everything else. The lock is only as strong as the screws holding it to the door and the jamb, and the rim cylinder on an old one is often the weakest part of the assembly.
A jimmy-proof deadbolt interlocks the door with the jamb using vertical bolts and resists prying. A police lock is a steel brace running from a socket in the floor to the back of the door, resisting battering by carrying force into the floor instead of the frame. They stop different attacks, which is why many New York doors have both.
Yes. The outside cylinder is a separate rim cylinder, so it can usually be rekeyed or swapped on its own without touching the lock body. It is also the moment to consider a high-security rim cylinder with a restricted keyway, which stops casual key copying. Call (718) 412-1332 if you want it quoted for your door.
Usually not. The common cause is that the door has sagged or the frame has shifted, so the bolts no longer line up with the rings - an alignment problem, not a mechanism failure. Adjusting the hinges and the strike normally fixes it. Replacing the lock without correcting alignment just gives you a new lock with the same symptom.