Rekeying, explained simply
Rekeying changes the inside of a lock so the old keys stop working, while the lock itself stays on the door. It's the usual answer after buying a home, since there's no telling how many keys the last owners handed out. For a code instead of a key on the front door, see smart lock installation.
When replacement makes more sense
A lock that's worn, loose in the door or corroded from years of humid air is replaced instead. So is a light-duty deadbolt on a door that deserves better.

Front, back, garage entry and side doors, all on the new key.
All the locks set to a single key where the hardware allows.
Heavier deadbolts where the old ones fall short.


