Before the Level 3 bench, this door is built out of road runs. The metal fragments come from one furnace load, but the two gears can't be crafted yet, so they come from crates, barrels and the recycler. Plan the doors by the gears in the box: a loot room and an airlock already mean two doors.
Next to the sheet metal door it is a real step. That one is a default blueprint made of frags alone, and raiders open it with far fewer explosives. The garage door asks for gears and a wall frame, and in return holds noticeably longer.
Watch out
Don't feed spare gears to the recycler while doors are missing. A gear comes back as a little scrap and frags, and two of them were a door.
Once HQM flows, the armored door is the next step, and it eats gears even faster.
