Fusion recommends a Holiday Key for use on all Double-Deadbolts. This clever little key-turn is designed for use on the interior side of the double-deadbolt when you are home. This provides a quick and safe exit in case of a fire or an emergency when the door is locked. Before you leave and lock up the house, just take the Holiday Key out of the cylinder and stash it in a safe place until you return! It's the best of both worlds; the security of a Double-Deadbolt when you are away and the convenience and safety of a standard Deadbolt when you are at home.