The Clean/Dirty Sliding Sign can be directly installed on the door using the foam adhesive strip included with the sign. The top panel of the sign slides back and forth to reveal if the laundry area has clean or dirty clothes. Sliding Signs have the following benefits -  Two-in-one signage: The top panel slides back and forth to reveal only one status while hiding the other one.  Strong Construction - These signs are made from a 60 mil thick engraved plastic plate recessed within a solid anodized aluminum frame.