Sturdy Parcel Lockers are compatible and can be arranged in any order, depending on your needs, with lobby tables, 24" Rack Ladder Systems, and Rotary Enclosure Systems. The parcel locker key is placed in the recipient's mailbox when a parcel is delivered. When the locker is opened, the lock captures the key until it's released by the master key. The top lock space requires installation of postal arrow lock, and bottom lock is a tenant lock. For private use, a Master Commercial Lock must be utilized. Units have individual rear doors for added security. Door Size: 11"W x 15.5D x 11.75"H