I made a couple sets of slide in mudflaps for some guys at work. Used 1.75" square tubing, figured the depth and drilled through tube and receiver for a set bolt location. Put in nut plates for the flap attach points and anchor, trimmed a generic flap from the truck supply place, and capped the open end with an eye for a rope tie point. They wanted them so their camp trailers wouldn't get shot up with salty snow and gravel during hunting season.