Tarp Fence Sagging Green
While not as sturdy as solid concrete, iron constructions have high structural integrity, requiring fewer support pillars.
Harvest drops
Iron× 10
Taken apart with a harvesting tool (axe, pickaxe, shovel), before perks and tool bonuses.
When it collapses
Falling, it leaves 
Scrap Metal Pile (60% of the time) where it lands.
Where to find (29 POIs)
Navezgane Athletics Complex (tier 5), Ostrich Hotel (tier 5), Butcher Pete's (tier 4), Doominium Tower (tier 4), Downtown Marketplace (tier 4), Flushing Rule Palace (tier 4), Housing Development (tier 4), Atlas Metal Company (tier 3), Greg's Motel (tier 3), The Serrano Residence (tier 3), Bell Lake (tier 2), Federal Appliance (tier 2), Sweet Sweet Honey Pot Farms (tier 2), Crazy Billy's Used Cars (tier 1), Hook, Line, & Sinker (tier 1), Oskar's Dumpster (tier 1), Pass-N-Gas Store #01 (tier 1), Radio Outpost (tier 1), The Dead Rooster (tier 1), The Roland Residence (tier 1), The Smokehouse (tier 1), Bean Counter Court, Bruno's Boulevard, County Stockpile, Downtown Construction Site, Industrial Construction Site #10, Junkin, Leyline Electric Depot, Trader Bob.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.