Fences
Red Bandit Wall, Siding, 3x3
While not as sturdy as solid concrete, iron constructions have high structural integrity, requiring fewer support pillars.
Harvest drops
Iron× 17
Taken apart with a harvesting tool (axe, pickaxe, shovel), before perks and tool bonuses.
When it collapses
Falling, it leaves 
Scrap Metal Pile (75% of the time) where it lands.
Where to find (5 POIs)
Bill Gearz Place (tier 3), The Animal Hoarder (tier 2), Hybrid Energy Substation #4, John & Sons Construction, Trader Rekt.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.