Just doors rotated 90 degrees so you can use them for some neat stuff. I couldn't get the closing/opening animation to look perfect because the game isn't made for this, but they work just fine otherwise.
https://www.dropbox.com/s/4mkyahcblamal ... s.zip?dl=1
There's a readme, take a look at it.

lol use the hatches added in the new version instead

Quite a nice mod. Stalin approves.