Steel Door Double
Can be placed or used to upgrade a Iron Double Door.
Press & hold Activate to lock or set a combination. Repair with Forged Steel and a construction tool.
Upgrade path
Hit a placed block with a stone axe, claw hammer or nail gun while carrying the material of the next step.
Also upgraded from 
Black Iron Door Double (1× Steel Door Double), Blue Iron Door Double (1× Steel Door Double), Brown Iron Door Double (1× Steel Door Double), Green Iron Door Double (1× Steel Door Double), Grey Iron Door Double (1× Steel Door Double), Iron Double Door (1× Steel Door Double), Orange Iron Door Double (1× Steel Door Double), Pink Iron Door Double (1× Steel Door Double), Purple Iron Door Double (1× Steel Door Double), Red Iron Door Double (1× Steel Door Double), White Iron Door Double (1× Steel Door Double), Yellow Iron Door Double (1× Steel Door Double).
Crafting
Craft at Workbench · makes 1
Forged Steel× 10
Spring× 10
Mechanical Parts× 10
Harvest drops
Iron× 96
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 (9 POIs)
Area 7 (tier 5), Camp Hollow Point (tier 4), Installation Blue Ridge (tier 4), HNN Bank (tier 3), The Serrano Residence (tier 3), Duck Station (tier 1), HNN Bank Building, HNN Bank Ruins, Perk Penny Place.
Points of interest built with this block (any of its variants), the highest tiers first, from the game's prefab files.