I installed the molded mud flaps on my "base" 06 FEH...all four locations. The instructions that came with these OEM flaps were comprehesive and very helpful. I had no problems, if I remember correctly: the Ford flaps are pre-drilled and you fit them up to the truck and drill one hole for a new fastener at each of the four locations. All of the other fasteners are part of the wheel well already. You then remove all the fasteners and replace them in the same holes after inserting the new flap. After I was done, I stepped back to look at rear flaps and they seemed to be tilted at a slight angle....they were but it must be by design because the holes are pre-drilled (there is only one way they can go on). Anyway, having had all kinds of mud flaps on other cars, these molded ones look like they belong.