The bottom par looks like part of the base plate. You need the rest to attach it to the frame. I have a stowmaster that attaches to the same mount. You need the vehicle side of the mount and one of the options that hooks to the tow vehicle.
2010 Damon Daybreak 3204 Sport, bunkhouse with Jeep Wrangler toad.
Improvise, adapt and overcome... "Semper Fi"