This is a popular fifth wheel jaw hitch, for connecting to the king pin of any RV fifth wheel trailer. It mounts in the middle of the bed of the truck, over or slightly ahead of the truck's rear axle.
http://www.etrailer.com/tv-Demo-B-and-W-Fifth-Wheel-BWRVK3270.aspxThis is fifth wheel king pin, which welds under the pin box (tongue) of fifth wheel trailers. This king pin slides into the hitch's jaws, which then close around king pin, nesting into that detent groove around the middle of the king pin.
http://www.etrailer.com/Fifth-Wheel-King-Pin/Wallace-Forge/T809.htmlThis is a farm/utility/atv pull-pin hitch, also called clevis pin hitch. This is the part that slides into the trucks receiver hitch, under the bumper.
http://www.etrailer.com/Clevis-Hitch/Convert-A-Ball/AMCC2.html