For all you guys recommending someone buy a flanging tool, please watch the following video and see what can and will happen in a flanged repair. This is a tailgate on a wagon that had the lower skin fixed with a flanged seam. The ghost line shows exactly where the repair was made.
https://www.youtube.com/watch?v=OGhFEfVqxb0
Now that you have seen this, please stop recommending someone buy a worthless gimmick tool without cautioning them of the hazards of such a repair. You are welcome to link my video in doing so, please! Or, just stop recommending the tool altogether. There are many other tools that someone can better spend money on, all while BUTT welding the seam with much better results.