Fender Rolling Tool

^ has it all figured out

it works great and looks killer as well. Round solid rod is also good on any area you have to add sheet metal..

I tried the above method except I used 3M panel adhesive to hold the rod in place once I had it formed to match the lip. I didn't want to deal with welding the extremely thin fender for fear of warpage(it was a Mazda, btw) After it was glued in I ran a bead of seam sealer around the top edge to give it a finished look and seal out moisture. It worked out very well, I will be doing it to my Hilux when I can find a decent pair of fenders for it.