Safety and securely keep your spare key(s) for your home or apartment. Just like the units used by realtors for years now. Cahngeable four digit combination is user-selectable and can be quickly and easily changed as often as you like. The large locking steel loop attaches to door knobs, fences, railings, pipes and much more. Share the combination with only those you want to allow access - family members, friends, neighbors, emergency personnel, housekeepers, workmen and much more. Never be locked out again!