I have been working on a project for my engineering class. I have been modeling a F-117 Nighthawk stealth plane from a small model which I have.  I created a 3d sketch as a sort of skeleton and then created a block around it which I carved up to create the body of the plane.  The problem is my teacher says I need to define this sketch but it is nearly impossible. Is there a way to do this which I don't Know about???  Please help.