I have a problem i hope is not too hard to solve, i just dont know how right now. I have spaces in my map which portals can be placed on, but i do not want the player to be able to place portals there. So, is there some kind of texture or anything that prevents this problem?

Func_Noportal_volume
A 1 unit invisible texture over the wall

I found many topics about this, next time, search first

i will, and thank you