Fences
Grey 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)
Two Bit Tower (tier 5), ChemTech Distribution Center (tier 4), Dumpsy Clinic (tier 4), Favales Academy (tier 4), ParKing Garage #2 (tier 4), Fortified Farm (tier 3), The Johansen Residence (tier 2), The Wagner Residence (tier 2), Caravan Carousel (tier 1), Radio Outpost (tier 1), The Simmons Shanty (tier 1), Trader Bob, Trader Rekt.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.