Lock Guide
Most New Yorkers carry more keys than doors they actually own. A typical ring holds a building entrance key, an apartment deadbolt key, a second key for the latch or knob, a mailbox key, and something small for a bike room or a storage cage. Half of those open doors you have no authority over. The other half open locks sitting six inches apart on the same door, for no better reason than that they were installed at different times by different people.
Keying those locks alike is one of the quieter things a locksmith does, and it is routinely misunderstood. This guide covers what keyed alike actually means, which of your keys can realistically be combined in a New York City apartment, how it differs from a master key system, and the tradeoff you are accepting when you put everything on one key.
Keyed alike means two or more locks have been set internally so that one key operates all of them. The work happens inside the cylinder, not on the key. A locksmith removes the plug, changes the pin stack in each lock to a single shared combination, and cuts keys to match. Afterwards every lock in the set accepts the same key and rejects the old ones.
That is worth stating plainly because the common assumption runs the other way. People sometimes imagine a universal key, or a key cut in some special way that will open several different locks. No such key exists for ordinary hardware. If one key opens three locks, it is because someone deliberately set those three locks to the same combination. The change is to the locks.
Every cylinder has a keyway, which is the shaped slot the key blade slides into. Different manufacturers use different profiles, and a blade cut for one profile physically will not enter another. This is the first question a locksmith asks when you say you want one key for everything: do your cylinders share a keyway?
In a NYC apartment it is common for the answer to be no. The deadbolt may be one brand, the knob or lever another, and an old secondary lock a third. Where the keyways differ, the fix is to replace the odd cylinder with one that matches the rest, which is usually inexpensive because only the cylinder changes rather than the whole lock body.
Once the keyways agree, the rest is routine. Each lock is rekeyed to a chosen bitting, which is the pattern of depths cut along the key. Locks with different pin counts cannot share a bitting, so a five-pin cylinder and a six-pin cylinder cannot be brought onto the same key without replacing one of them.
If the idea of changing what a lock accepts is new to you, our guide to what lock rekeying is walks through the mechanics, and rekeying versus replacing a lock covers when a cylinder has to go rather than be reset.
This is where expectations and reality separate, and it comes down to who owns each lock.
The locks you own are the ones on your own apartment door, plus anything inside the unit such as a closet or an interior door, plus padlocks you bought yourself. These can almost always be brought onto a single key. For most tenants and owners that means the deadbolt and the latch finally share one key, which is the change people feel most, because it is the pair you fumble with every day.
The locks you do not own are the building entrance, the service door, the laundry or compactor room, and the common areas. Those cylinders belong to the building, and changing them is a decision for the landlord or the managing agent, not for you or your locksmith. They also usually sit inside a building-wide keying plan, which brings its own constraints.
The mailbox sits in between. Tenant mailbox locks in a NYC multiple dwelling are generally the landlord's responsibility to maintain, and the postal access lock on the bank of boxes is not anyone's to touch but the Postal Service. See mailbox lock replacement in NYC before assuming that key can join the set.
So the honest outcome for most apartments is this: one key for your own door, one key for the building, and a short ring instead of a long one. That is still a meaningful improvement over four keys that all look alike in a dark hallway.
These two get confused constantly. Keyed alike means several locks share one key, and that is the whole arrangement. A master key system is hierarchical: each lock keeps its own individual key, and a separate master key opens every lock in the group, with sub-masters in between for a floor or a department.
Buildings, offices and schools need the hierarchy because different people get different levels of access. A household almost never does. If you are a landlord or a managing agent wondering which you want, start with master key systems in NYC buildings, which covers how the levels are planned and where they go wrong.
One key is more convenient and slightly more concentrated as a risk. If that key is lost or stolen, everything on the set is exposed at once, and the recovery work is larger than it would be for a single lock. Our guide to lost apartment keys in NYC covers what that recovery looks like.
There is a real argument on the other side. People with too many keys start taking shortcuts: leaving the back door unlocked because the key is a nuisance, handing out copies they then lose track of, or hiding a spare somewhere obvious. A single key people are willing to carry often produces better behavior than a ring nobody wants to deal with. If you are tempted by a hidden spare, read key lockbox safety in NYC first.
The sensible discipline is to decide deliberately what belongs on the set. Home locks together, yes. An office, a storage unit, or a business back door on the same key as your apartment, no. Those should stay separate so that losing one does not compromise the other.
Keying alike works the same way inside a high-security system, with one important addition. Restricted keyways mean blanks are not sold over the counter, so duplicates can only be cut by the authorized dealer against a signed record. You get the convenience of one key without the usual downside that anyone holding it for ten minutes can make copies.
That combination suits a small business owner, a landlord with a handful of units, or anyone who has had a key walk away. See restricted keyway locks in NYC for how key control is actually enforced, and key copying in NYC for what can and cannot be duplicated.
A locksmith starts by looking at each cylinder to confirm the keyway and the pin count, which takes a few minutes and decides whether anything needs replacing. The cylinders are then removed, rekeyed to a common combination, and reinstalled. New keys are cut and, critically, tested in every lock with the door both open and closed, because a cylinder that turns on the bench can still bind once it is back in a door that is out of alignment.
Worn hardware is the usual complication. A cylinder with heavy wear, or a lock that was already sticking, will not improve because it has been rekeyed. If a lock is close to the end of its life, replacing it now while the locksmith is already on site is cheaper than doing it twice. The signals are covered in signs your door lock needs replacement, and if you are choosing new hardware, the best lock type for a NYC apartment is the place to start.
Your apartment entry door faces a common corridor, which is why hardware changes on it are not always purely your business. Co-op boards and managing agents frequently require approval for anything that alters the door or its visible hardware, even when the work happens inside your unit. Rekeying an existing cylinder is usually treated as routine; swapping a cylinder for a different brand sometimes is not. See co-op board approval for door hardware and changing locks in a co-op versus a condo.
If you rent, check your lease and talk to the landlord before keying anything alike, particularly if the landlord holds a key for access. Who pays is a separate question, covered in whether the tenant or the landlord pays the locksmith.
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Yes, when the cylinders share a keyway and the same pin count. Where they do not, the mismatched cylinder is swapped for one that matches, then every lock is rekeyed to a single combination and new keys are cut for the set.
No. Keyed alike means several locks accept one key and nothing more. A master key system gives each lock its own key plus a higher-level key that opens the whole group. Buildings need the hierarchy; a household almost never does.
Almost never. The entrance cylinder belongs to the building and sits inside a building-wide keying plan, so changing it is a decision for the landlord or managing agent. The locks on your own apartment door are the part you can bring onto one key.
It concentrates the risk. Losing that key exposes every lock on the set at once. Keep your home locks together and keep unrelated locks, such as an office or a storage unit, on a separate key so one loss does not reach both.
Yes. Restricted keyway systems are routinely keyed alike, and the key control that comes with them means blanks are not sold over the counter and duplicates are cut only against an authorized record.
Rekeying is enough when the cylinders are in good condition and share a keyway. New cylinders are needed when keyways differ, when pin counts differ, or when a lock is already worn enough to be sticking or binding.