Rekeying a lock is replacing the old lock pins with new lock pins. Locks are usually re keyed to build master-key systems, make a set of locks share a common key, or to eliminate compromised keys.

Is it cheaper to rekey or replace locks?
Due to the extremely low price of the key pins in the locks, rekeying is almost always much cheaper than getting your locks changed. … For example, if your home has several locks and each lock has a different key, which can be inconvenient, you may want to rekey the locks to all match the same key.