My first question is about the rebuild surface function. I wanted to know what exactly is its base purpose? Rearranging the isoparms/cvs more uniformly within the patch? Or does it have some other hidden purpose as well?

My second question is, of course, related to those very troublesome trimmed surfaces. In the rebuild surfaces options i've noticed the trim convert feature. I checked the documentation but all it says is that it "Rebuilds a single-region trimmed surface (with four boundary curves) into a non-trim surface." I tried on a trim surface (the hexagonal bolt one for instance ) and it gives me the following error: "Rebuild surface failed on the current valid selection."

So how exactly does it work? Because it would be real nice if i could convert a trimmed surface into a normal patch again. That would mean it could also be trimmed multiple times, which would be nice.

I would appreciate any help, as these nurbs seem to be really complicated.