Armored Double Door

You only need this one if your base has a double doorway. It goes into a wide wall frame, the same opening a garage door fills, so once you have built one for a big entrance, this is what closes it at the top tier.

Next to the single armoured door little changes: the same Level 3 bench, the same 120 scrap to research, the same five gears. The difference is 25 high quality metal instead of 20, and the recycler hands a bit more of it back. Both carry the hatch to look and shoot out of. As far as players can tell, the wider door does not take more explosives to open, so a double frame costs you HQM and buys no extra safety.

The usual path is simple. Early on, a sheet metal double door fills the frame for frags, and when the Level 3 BP comes in you swap it for this one. The typical story: the wide front entrance went up on day one because it looked good, and now every upgrade costs five HQM more than on a single frame. If you are still planning the base, single frames on the way to the TC are the cheaper call.