Is there a diagram available that shows what all the empty holes are intended for? The larger holes in the corners I utilized by putting in Marine stainless steel eye bolts, ( work well and look nice/clean). In the side walls there are some 3/8" hexagon shaped holes, but the metal is very thin there. What is supposed to snap into those holes? Are there snap ins available. I use a cargo net and I want to utilize those holes to add smaller eye bolts for the sides of the netting to clamp onto. Any suggestions? Thanks