Does anybody have any pictures are how to make the middle hinge on a folding ramp. I am trying to make a ramp for my box truck but want it to mount flush so I can have a hitch and not have any extra length to the truck. There are a lot of things to buy but I know I could make the same thing just not sure how they are doing the folding hinge and it be heavy duty enough to hold around 1800 pounds.