Many locksmith, landlords and property management companies re-key locks or "change" locks. The principle of Re-keying locks is very simple. Re-keying a lock is changing the key combination of the cylinder you are working with. For example you are re-keying a Kwikset lock with a combination of 23135 and a new key with combination of 14552. The cuts aren't similar enough for the old key to open the lock with the new combo.