HO/O-SCALE DOG HOUSE BILLBOARD-HO/O-Scale. HO/O-Scale. Great for summer! This sign is unique in that it has the ability to be mounted two different ways! - (1) regular roof top billboard; or (2) because a second set of contacts to the backside center, it can be mounted flush against the front or side of a building. When mounted flush, the regular supports and lower contact are trimmed off. Sign measures approximately .64" x 3.35". This is a Limited Edition Sign!