NEVER use the clipping (aka carve) tool. Trust me it is evil and will fuck your maps up. Slice tool is a much better option. Select it (second bottom tool i think) draw two spots on the item you want to slice then hit enter. The red bit will be deleted and the white kept. By clicking the tool icon again it will change between keep right and del left, keep left and del right and keep both. Very easy to use.
Ladders are easy. Make a brush of what you want to be a ladder. Hit ctr + t then select func_ladder. Done.
Edit: I think your talking about the slice tool.