Tarp Fence Falling Right Blue
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 (22 POIs)
Butcher Pete's (tier 4), Doominium Tower (tier 4), Housing Development (tier 4), NDC Checkpoint One (tier 4), Atlas Metal Company (tier 3), Mamma Pizza (tier 3), Shady Woods Amphitheatre (tier 3), Maggie's Corner Cafe (tier 2), McPherson UFO Museum (tier 2), NC Bus Repair Site (tier 2), The "Broken Dreams" house (tier 2), Camp Deucenhalf (tier 1), Hook, Line, & Sinker (tier 1), Oskar's Dumpster (tier 1), The Roland Residence (tier 1), The Smokehouse (tier 1), Cleanico Center, Downtown Construction Site, Industrial Construction Site #12, Junkin, Rhythm & Brews District, Trader Bob.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.