Do Not Enter Signs

Mount it on the door or the wall at the entrance, facing people who walk toward it. Place a second sign at the opposite end of a long corridor so people entering from either side see the rule. Check local code or site rules for any sign that marks an exit or fire route.

Pick danger (red) when crossing the threshold would expose someone to a gas-filled space, a collapse risk or a similar threat that could cause death. Choose notice (blue) for a closed office, a storage closet or any room where no hazard message applies. The hazard inside, not the strength of the rule, decides the header.

A 12 x 18 in portrait sign suits a door window or a narrow wall beside a frame. For a hallway end or a wide opening, a 24 x 18 or 36 x 24 in landscape sign is easier to read from across the room.