All about Rekeying
Rekeying is a method of making new keys by disabling lock tumblers of pad locks or locks where old pins are replaced with new ones.
When rekeying a lock there is a replacement of the pins that were there before with some new ones and the locks are normally done so to either master-key or re-key so as to stop any keys getting compromised.
Pins of the lock may be worn out and they require replacement with ones and there are cases where the pins may get shorter and cannot reach the shear-line and so when the key is used it cannot open the locks.
Older keys cannot open other locks that are not similar and thus there is need to know what kind of key is to be made for a particular lock and many manufacturers give specific manuals for each particular lock and key.