in gmod, a door is called borealis door in the spawn menu, one of the first items when you open in, and if you search borealis in the spawn menu, you will find 3 barrels, one higher quality than the other, and another one that's crumpled, you'd also find a valve and a weird object that i cant really describe.
That's because these models are leftovers from early development. The Borealis in Half-Life 2: Episode 2 was a reused concept that was scrapped in Half-Life 2.
If you have extended spawnmenu and hl2 mounted you can find a folder called props borealis thats where they are.