STOP, did you forget something?

These three little molded/engraved plaques are examples of similar little signs that used to be commonly found fastened just inside any odd hotel/motel room's door, as a reminder for the occupants. Each measures about 4" long, and is made of either black or white plastic with engraved and filled lettering. I've found them in various other places over the years, perhaps indicative of the reasons why they're seldom found in today's motel rooms...??