Rekeying is the process in which the key pins inside the lock are changed by a locksmith. As a result, a new key will be used to open the lock, and any old keys will no longer work. Rekeying is imperative because there may be copies of your key that you may not even know about, especially if you bought a new home, had employees leave your business, etc. Rekeying is also more affordable option than replacing a lock.