I know that Kwikset made some locks that you could re-key yourself. I believe you needed to use the original key for the lock and turn it, then use the special key designed for rekeying and turn it at a different increment, then put in the new key that you wanted it to be keyed to and turn it a different direction. Schlage locksets can also be re-keyed but it is a little more complicated and Schlage makes sturdier locks.