hinge. the hinge is made of cat D8 cutting edge bolt washers that are stacked and boxed in with two peices of angle. they are welded to the bottom frame. the pin is 1 1/8" and is welded on the ends to the bed with 5/16" flatstock & 1/4" thick square tube on the inside of hinge to give more surface area to weld on, & of course a grease fitting.