Bed crossmembers or supports. You can see the large holes on the top which allow a socket to be used to tighten the supports to the frame with 1/2" bolts. The middle support I had to elongate the access holes to tighten the wood bed strip bolts because it is right above a factory crossmember. This could have been avoided but I wanted equal spacing on the bed boards. You can also see why I need to have wheel spacers made...This is a GMC bed which is 2" wider than Chevy. I have 1/2" clearance between tire and bed side. Had I only known before...
