Cutting Away Floors/Surfaces

[theRBstream]

Ahoy hoy. Apologies if this has already been asked, but I haven't found it in my search.

Is there a way to cut away a section of flooring? I'm creating a 'fighting pits' area in a casino where there is basically a hole in the floor revealing the arena below. So, while I could duplicate the sandy floor of the arena and have one in with my layers on the above and expand the way it's set up on the other layer, it would be more convenient to just cut it away.

This would also be helpful for the sake of a bar, which I also often find myself using the flooring tool to create.

[theRBstream]

Also, adjacent to the original question, is there a way to turn wall shadows to be, for lack of a better term, internal only?

[sheep from hell]

here is an video about it

https://www.youtube.com/watch?v=smaOlygBzI0

for the wall question, you could seperate the walls with and without shadows in two seperate groups and create shadows only for the group when they are internal