Decor and furniture
Sign Canvas Corrugated Metal 11x6
It's a sign. You write things on it.
Harvest drops
Iron× 10
Taken apart with a harvesting tool (axe, pickaxe, shovel), before perks and tool bonuses.
When it collapses
Falling, it leaves 
Scrap Metal Pile (60% of the time) where it lands.
Where to find (3 POIs)
Doominium Tower (tier 4), Richard Munchz Plaza (tier 4), Corona Wipes Billboard.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.