Big waste of money Brangdon to change a lock. To match the two locks to one key, just take the other lock to a locksmith and have the pins replaced to match. In a similar case where you just purely want to change the locks to keep your ex-wife out or whatever, take both locks to a locksmith and have a pin or two rearranged and get the appropriate key to match. Much cheaper than changing locks, especially if you are dealing with an expensive commercial lock. In the scenario you describe with a matched pair and a lost key, no problem. Again, take one of the locks to a locksmith and have a key made and presto, you again have a set of matching locks with a key. In the case of keys, any key, I ALWAYS have a back up. In some cases, a backup to the backup. It is much too easy to lock your keys in the car. <img src="/images/graemlins/smirk.gif" alt="" />