Fences
Green Bandit Wall, Ribbed, 3x2
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 (13 POIs)
ChemTech Distribution Center (tier 4), Wasted Stiff's (tier 4), Ranger Station Alpha (tier 3), The Wagner Residence (tier 2), Cabin Retreat (tier 1), Camp Deucenhalf (tier 1), Hog Foot Village (tier 1), The Simmons Shanty (tier 1), ParKing Lot, Trader Bob, Trader Jen, Trader Joel, Trader Rekt.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.