Doors and hatches
Fake Cabinet Door 1x1.5 Concrete
Zombies can see through this block. The intended use is that a hidden zombie can see the player and bust out of a closet.
Harvest drops
Small Stone× 25
Taken apart with a harvesting tool (axe, pickaxe, shovel), before perks and tool bonuses.
When it collapses
Falling, it leaves 
Destroyed Stone (75% of the time) where it lands.
Where to find (1 POIs)
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.