sloped half-wall

[MarkST]

Louis, or someone

That thumbnail at the top is exactly what I am trying to do. I think I saw a thread on putting the railing on the wall, but how do I cut the wall like that? I already have the stairwell rendered fine. The client asked for one side to be cut open and the railing exposed to the dining area. I can't figure out how to cut the opening with that angle.

After that, I'll try to figure out how to put the railing on the sloped wall top.

Can someone give me a little direction? I'm not a newbie, but I haven't tried this before.