some kind of rustoleum black gloss auto paint.6x 5/16' machine screws with a conical head and 3/16' hex top (fits into a conical countersink for flush mounting).4x Grizzly G9514 T-slot nuts or 4 1/2' carriage bolts (both fit real well but carriage bolts don't slide very easy, consider them a more permanent install).This was very time consuming, but I think over the lifetime of my truck and toolbox this will more than pay for itself in time saved, busted knuckles, and cursing at my stupid toolbox while trying to pull it out in the winter with numb hands so I can help so-and-so move their gigantic sofa across town. I can put my toolbox on and take it back off in 5 mins and it's held on very securely, way better than any OEM attachment I've ever seen. Click to expand.I made one like what you describe and I'm real happy with it.