Tot Lok is a magnetic locking system that keeps cabinets and drawers closed to children. This extra key has a powerful magnet that deactivates the lock. It is helpful to have an extra key for convenience and in case of loss. Works on cabinets from 1/2" thick to 1 9/16" thick. If you have dense wood or thick cabinets you should consider item 71172-ES an Extra Strength Key.