I marked the holes on the flair with a 3 inch compass as Rusty did, but drilled them in the flairs first. Then I used "C" clamp type vice grips to clamp and adjust on the fenders to my liking, making sure they were parallel with fender seams and the same distance from them at the top. Then I made sure the DS and PS matched the distance from the ends of the fenders and quarter panels on both sides. Once I was happy, I drilled through one of the holes in the flair and into the metal, put a 10-32 button head screw in, then started working my way through all the holes.