When you move in and can't account for the old keys, the key that opens your locks should change. Copying the keys you were handed won't stop the copies you never saw. Rekeying keeps the existing lock hardware and changes the key it accepts. Replacing swaps the hardware. Which fits depends on the condition of the locks and how many doors are involved, not on how many keys exist.
Why the number of old keys doesn't change the decision
At move-in you usually get a few keys and no record of who else got one. You can't find out, and you don't need to. Whether two copies are out there or twenty, each one is a key you don't control, so the fix has to make all of them stop working.
Copying the keys you were handed doesn't help. A duplicate is cut to the same pattern as the original, so it opens the same lock as every unknown copy. Copies are useful after the key changes, not before.
Rekeying keeps the lock and changes the key
In locksmith terms, rekeying means changing the key a lock accepts while the lock itself stays on the door. Inside the cylinder, the part you slide the key into, sits a row of small spring-loaded pins of different lengths. The right key lifts each pin to the height that lets the cylinder turn. Rekeying swaps those pins for a new set, so a differently cut key lines them up and the old keys no longer do.
The lock body, its finish, the knob or lever, and the way the door feels when you lock it all stay the same. What changes is the key: every old one stops working, and new keys are cut to match.
Rekeying suits a lock that already works well. The key goes in and turns without forcing, the bolt moves fully, and nothing is loose or cracked. If your locks behave like that and you like how they look, there's little reason to throw them out.
Replacing the hardware: what you gain and give up
People call both options changing the locks, but only replacement swaps the lock itself. A new lock has its own keys, so the old keys stop working for the same reason they do after rekeying. What sets replacement apart is everything else it lets you fix.
Replacement makes sense when the lock has problems a new key won't solve. A cylinder that sticks, a bolt that drags, a lock body that wobbles on the door, or pry marks from a past forced entry are hardware issues. Rekeying a worn lock leaves you with a worn lock that takes a new key. Replacement is also how you deal with mismatched locks when you want every door to look and work alike.
The trade-off is more change to the door. New hardware has to fit the holes already cut in the door and frame, and it can look and feel different from what you had.
Which one do your doors need?
How each lock behaves today tells you the most. Lock and unlock it a few times with the door open, then with it closed. A key that turns smoothly with the door open but drags when it's closed usually means the door is rubbing or the bolt isn't lining up with the hole in the frame, not that the lock is failing. A key that drags either way points to the lock itself, and toward repair or replacement.
Damage matters more than looks. Worn finish is cosmetic. A bent bolt, pry marks, or a cylinder that spins loose in the door are not.
Mismatched locks matter if you want one key for the front, back, and side doors. That only works when the locks share the same keyway, the shaped slot the key slides into. Matching locks can usually be set up to take one key. Locks of different makes or styles often can't, and replacing the odd ones out is how you get to a single key.
Multi-door and commercial properties add a layer. A property manager with several units, or a business owner with offices and storage rooms, often wants each door on its own key plus one key that opens a group. That arrangement is a master key system, and it's worth planning before any locks change so the hardware fits it.
Safety Locksmith works on lock repair and restoration, residential and commercial locks, key duplication, and master key systems. To talk through your doors and locks, call (347) 666-4989. It helps to have this ready:
- How many doors, and what kind of lock is on each, such as a knob, lever, or deadbolt
- Any lock that sticks, drags, wobbles, or shows damage
- How many keys you were given and which doors they open
- Whether you want one key for all doors, or a master key arrangement for several units
Frequently asked questions
Is it worth keeping the old keys as spares after the locks are changed?
Old keys aren't worth keeping once the locks are rekeyed or replaced. They open nothing, and a drawer of dead keys makes it harder to tell which ones still work. Spares should be cut from one of the new keys instead. Safety Locksmith offers key duplication for those extra copies.
Should I handle the exterior doors and interior or secondary locks at the same time?
Exterior doors come first, because any old key to them opens the home. Interior and secondary locks, such as a home office, a storage closet, or a shed, have the same unknown-key problem if keys to them were ever handed out. Dealing with all of them at once also makes it easier to put several doors on one key, if that's what you want.
As a property manager, how do I avoid carrying a separate key for every unit or door?
A master key system gives a property manager one key that opens a group of locks, while each unit or door keeps its own key that opens only that door. Tenants and staff carry just their own key, and the manager carries one instead of a full ring. Safety Locksmith works on master key systems.
What should I do about a door whose lock has no markings or won't accept any key I was given?
A lock with no markings, or one that won't take any key you were given, should be treated as having unknown keys in circulation. Forcing a key into it can damage the cylinder, so leave it alone. Note which door it's on and what type of lock it is, and mention it when you talk to a locksmith. A lock nobody can operate is often a candidate for replacement.