now you have to select the texture 'Ladder' which can be found in common textures and apply it to the brush. The trick is 2 have it in front of the actually ladder and not going over the back of it like so (look at picture) if u have the ladder texture go off the back aswell it means u can climb up the back of the ladder which is bad lol

Now for a different situation where u can use the ladder texture:

create a vines texture found in 'global_use' and place against the wall using the smallish grid setting (1)

around the edges of the vines u need 2 use the 'nodraw' texture so u dont get any crappy vines on the sides which will look crap in game, this texture can be found in 'common'

last step, select the vines and copy and paste it in the same spot, while u still hav this selected, select the 'ladder' texture and place it on the brush

and both ladders should work fine in game

Tutorial By Lurtz