A Deadbolt and Latchset combination where the deadbolt is locked and unlocked by a key on the exterior and by a turn piece on the interior of the lockset. Single Cylinder locksets are the most common used in residential applications.

A Deadbolt and Latchset combination where the deadbolt is locked and unlocked by a key on both the interior and exterior of the lockset. **Double Cylinder locks on doors used for exiting a building or a home are a life safety hazard in times of emergency and are not recommended**