Consider this a public service announcement.
The Kwikset smartkey lock has some good features. Homeowners can rekey the lock themselves (if you carefully follow the instructions), and the lock is pick resistant and bump resistant. It has a higher level of security than its older brother, the pin tumbler lock.
However, these features come with a risk. This lock will suddenly stop opening with your key leaving you locked out. If you have more than one door that uses the same key, you will still be able to get in. But if it is the only door available for you to use then you are locked out. What happens is the lock “rekeys itself” to a different key than yours. It is my un scientific observation that this happens more often when the owner is using hardware store duplicate keys that might be out of tolerance.
You can quickly determine if you have a smartkey lock by checking to see if there is a small slot (see picture) to the side of the keyhole where you insert your key. The slot might be on the other side if your lock was installed upside down.
If this happens to you, call me. I can get in with no damage and I can reset your lock and make you some factory original keys so that the problem wont repeat.