Fences
Grey Bandit Wall, Ribbed, 2x1
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)
Minotaur Theater (tier 5), Beanthere Coffee Company (tier 4), ChemTech Distribution Center (tier 4), Favales Academy (tier 4), Bill Gearz Place (tier 3), Booze Hound Brewery (tier 2), NC Bus Repair Site (tier 2), The Animal Hoarder (tier 2), Hog Foot Village (tier 1), Mercy Point Camp (tier 1), Philip Powers Residence, 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.