Mapping/Wallbreak

Step 1 - assume this is given

Step 2 - copy or create a new brush like this one

Step 3 - now hit the CSG-Substract toolbar icon or hit Shift U

Step 4 - copy or create a new brush - enter edge mode editing by hitting e and move around the edges like you see here

Step 5 - now hit the CSG-Substract toolbar icon or hit Shift U

Step 6 - move around the edges a little to get another shape to cut out of the wall - and cut them with the CSG-Substract toolbar icon or hit Shift U

Step 7 - move around the edges a little to get another shape to cut out of the wall - and cut them with the CSG-Substract toolbar icon or hit Shift U

Step 8 - check whether actor can go through the break - if not - move the wall break brushes to let him pass through