When I bought this house it had been a rental over a dozen years, so new keys were essential. And not just doors - this part of town has ornamental iron grates over most house windows and each bedroom window has a lock for obvious safety reasons. The back iron gates over sliding glass door had a key that fit all of them, but they barely moved due to inattention. So the locksmith rekeyed two regular doors, the security door, and three bedroom window grates. There was a key made to go in each room, hung from a cup hook under and beside the windowsill where each room occupant knew how to find it and work it. And there are spares in the drawer in the kitchen where all of that kind of thing goes.