I'm just getting the hang of modeling but I have a lot of trouble with complex shapes. I don't like using planar surfaces because they are just trimed planes which is cheap and cumbersom.

Currently, the only way I know how to 'put a lid' on a shape is planar as seen here in this mesh built with one bi-rail for the sides and a planar surface for the top (selected).


This of course causes problems when it's time to cut and sew it all together. Because of the planar surface, I can't further trim other shapes out of it.


Can you guys give me a few pointers on either patching or making trimable shapes? Thanks ahead of time.