Pin and Tumbler Lock – How to Compare with a Yale Lock

take the lock to your local home store that carries this line of locks. they will remove the core and put it in a SmartKey Reset Cradle. this returns the lock to an unprogrammed state.

there is no way to do this yourself without disassembling the lock core, and there's about a bazillion point 2 pieces in there.

You can have a locksmith rekey the locks, or you could even do it yourself with a rekey kit. To do this the cylinder will be removed, and the pins within it either replaced with different ones, or in theory they could just be swapped around. After this, the old key will no longer open the lock. You will need a new key. This must either come as part of the rekey kit, or one could be cut based on the new pin arrangement in the cylinder.

Do it yourself rekey kits are available for some lock brands online.

Schlage has a rekeying manual online that you can read and decide if it is a task you want to tackle or to leave to a locksmith. I would expect a locksmith to do it fairly inexpensively if you're able to bring the lock sets into the shop.