Quote Originally Posted by wirlybird View Post
What program would you use to modify a STL file? Say I have a basic cell phone cover and want to make a few minor changes such as add a design cutout to the back. I have Fusion 360 but haven't really got started with it yet!.
Try Meshmixer. It's a free download, works well with fusion and has a bunch of nice tools for editing existing models and cleaning them up.