Black Iron Hatch
Press & hold Activate to lock it or set a combination. Upgrade & repair with a construction tool using the secondary action.
Upgrade path
Hit a placed block with a stone axe, claw hammer or nail gun while carrying the material of the next step: 6 hits per upgrade.
Crafting
Craft at Backpack · makes 1
Crafted as Iron Hatch: pick this one of its variants when you place it.
Forged Iron× 10
Harvest drops
Iron× 20-30
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 (58 POIs)
Crack-a-Book HQ (tier 5), Navezgane General Hospital (tier 5), Pop-N-Pills Factory (tier 5), Red Mesa Compound (tier 5), Two Bit Tower (tier 5), Dumpsy Clinic (tier 4), Flushing Rule Palace (tier 4), Holvez Rent-a-Car (tier 4), Hotel Zombona (tier 4), Infested Warehouse (tier 4), Joe's Junction (tier 4), Judy Witch (tier 4), Navezgane High School (tier 4), Richard Munchz Plaza (tier 4), Super Shamway (tier 4), Town Hall (tier 4), Water Works (tier 4), Bob's Boars & Carl's Corn (tier 3), Haulwell Freight (tier 3), Le Spank (tier 3), Pop-N-Pills (tier 3), Savage Country (tier 3), Seemore Bank (tier 3), Shady Woods Amphitheatre (tier 3), The Boobie Trap (tier 3), The Rejekts Gang Outpost (tier 3), Working Stiff Superstore (tier 3), Bart's Salvage (tier 2), Fire Station 7 (tier 2), Joey's Carlot (tier 2), Oreally Auto (tier 2), Red Ruby's (tier 2), Shady Square Shoppe (tier 2), Shamway (tier 2), Smithstone Silos (tier 2), The Cartel House (tier 2), Am-I-Gone Funeral Home (tier 1), BJ Welding Company (tier 1), Bob's Cafe (tier 1), Metal Works (tier 1) and 18 more.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.