[RUNGSI]

Caulk is a texture the keeps the brush a solid but does not draw the surface.
You should always build your structures with caulk and then aplly the wanted texture to each side.
You only use textures on the sides that can be seen by a player while playing in game.
If you dont, the result will cause frame rate drops and removale of wanted surfaces.

say if you have a wall that butts against another wall, but you cant see the backside or top connections.
if you applied a texture to the whole brush on both, then as you play its drawing all sides of the brush even you do see them in game. This can cause frame drops.
Further more when 2 brushes intersect and all surfaces are drawn, the result will be even worse.
I construct all my structures with caulk first. Once the structure is complete I then texture each side visable but itself.

I only looked at his first version of the map. I noticed the laggy problem. I have not looked at any of the other versions. So I dont know how staligrad2 was built.