Hi Michael, I'm glad that solved it.

It can be easier in some ways to work on solids, because then you can cut a solid object up with Boolean commands and the various pieces of the cutting objects will stick around in the result keeping it a solid.

So for example if you have that revolved type shape, before you cut a hole in it it can be nice to seal off the end of it to make it a solid - there is a Construct > Planar command that will seal off planar openings like that.

Here's an illustration where I have a solid cylinder base object, and then I use the Boolean Difference command to cut a hole in it with the rectangle curve - note that the result in this case leaves the side walls that were formed from the rectangle extending out without needing to fill in those areas as a separate step:





- Michael