Factory Door

Choose it over a plain sheet metal door when you want to see who is standing outside before you open up. It is a skin of the sheet metal door, not a door of its own: you craft that one for 150 metal fragments with no workbench and choose this look if you own the skin, with nothing to research. The game's own text calls both medium strength and weak to explosives. What the factory door adds is a bulletproof viewing portal.

That window earns its place in a small base. You are sorting loot and hear footsteps on the porch: look through the glass instead of opening the door into a shotgun. It works both ways, though, so whoever is outside can see that you are home.

Bulletproof is not raid-proof. A few satchels treat it like any other door at this tier. Put a code lock on it, use it as a front door in the first days, and move the loot behind something tougher once your bench allows.