I have been trying to create an elevator in the default condo area and there is a patch of grass texture and models that cannot be removed in the way.
A block or cylinder that would cull existing models/textures and clipping or even a texture that can be added to an existing shape that would have a culling-type effect would be seriously useful for my issue and even for creating holes in existing shapes.
In my screenshot you can see the offending grass in the way of my lift and the same tool could be used to make a hole in the ceiling for the lift to go through without needing to create so many more primatives around it.