Metal Trussing Block
Metal trussing is quite sturdy and can be shot through.
Upgrade path
Hit a placed block with a stone axe, claw hammer or nail gun while carrying the material of the next step.
Crafting
Craft at Forge · makes 1
Crafted as 
Metal Trussing / I-Beams: pick this one of its variants when you place it.
- Iron (forge units)× 40
- Clay (forge units)× 5
Drops when destroyed
Iron× 1-15
When it collapses
Falling, it leaves 
Scrap Metal Pile (75% of the time) where it lands.
Where to find (66 POIs)
Area 7 (tier 5), Crack-a-Book HQ (tier 5), Dishong Tower (tier 5), Higashi Pharmaceutical (tier 5), Hybrid Mining (tier 5), Navezgane Corrections (tier 5), Navezgane County Jail (tier 5), Navezgane General Hospital (tier 5), Red Mesa Compound (tier 5), Shamway Factory (tier 5), Shotgun Messiah Factory (tier 5), Two Bit Tower (tier 5), U.S. Army Post #7 (tier 5), Camp Hollow Point (tier 4), Doominium Tower (tier 4), Flushing Rule Palace (tier 4), Fort Camo (tier 4), Fort Quonset (tier 4), Goldrush Station (tier 4), Green Hill (tier 4), Hotel Zombona (tier 4), Hybrid Energy (tier 4), Judy Witch (tier 4), Olgiddy & Brother Advertising (tier 4), Pete's Outlet (tier 4), Richard Munchz Plaza (tier 4), Stand Tower (tier 4), Buy-N-Go Apartments (tier 3), Haulwell Freight (tier 3), Hexagon Hideaway (tier 3), Jack's Lumber Mill (tier 3), Johnnytown (tier 3), NPD 3rd Division (tier 3), Ranger Station Alpha (tier 3), The Serrano Residence (tier 3), Aldos Cabinet (tier 2), Bart's Salvage (tier 2), Fire Station 7 (tier 2), Navezgane Creamery (tier 2), NFD Engine 4 (tier 2) and 26 more.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.