Doors and hatches
Loose Concrete Plate
A false floor or trap that will disintegrate when stepped on.
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 (7 POIs)
Vanity Tower (tier 5), Crumblemoor Catacombs, Figaro Square, Grasp of Silence Monument, HNN Bank Building, Mortabury Cemetery, Stable & Co Offices.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.