The Master Lock No. 5422D Portable Push Button Lock Box features a 3-1/8in (79mm) wide metal body for durability. The shackle design offers over the door mounting for convenience. Set your own 4 character combination for keyless convenience and increased security. The protective weather cover prevents freezing and jamming; and molded bumper and vinyl coated shackle prevent scratching. - Provides secure storage for keys, access cards - Set your own combination - Door knob mount