Fill in walls under the roof

- [Instructor] I'd like to use these two regions as tools…to help me cut back the walls.…You can see the walls currently don't rise up…to meet those roof surfaces.…We need to solve this problem first.…And knowing that I'm going to use these as tools…means that they're going to be deleted,…so I should think ahead and copy these in place.…So I'll say CO for copy,…select the two region objects,…and copy them from,…let's say the endpoint here back to the exact same location,…and then press Enter.…

This will effectively duplicate the regions.…I'm going to orbit under here…so I can see the top of this wall.…I'll hold down the Control key to access the subobjects…and then click on the surface to select it.…Now click on the blue arrow…and pull these walls up…somewhat above the wall surface, like that.…So now this extends above the regions.…Now I'm going to draw in a temporary line here…from the end of the ridge…up higher than the walls.…

Then extrude,…and I'm going to click once on each of these two regions.…I don't want to make a crossing selection…