Some pictures of how it was bolted on to the frame. The metal shop had added tabs to the cross bars that were about 2" x 3" and drilled 3/8 holes in them. At ATC we set the camper onto the cross bars and spent quite a bit of time lining the camper up to the cab. They then crawled underneath and began drilling holes through the 3/8" holes in the tabs into the camper floor. A special "flat head" bolt was then inserted through the inside of the camper and a washer and nut tightened on. The bolt head is about 1" or so in diameter and there is a washer under the head with tabs that grab into the floor so it does not spin while tightening (the bolt is square just under the head and the washer is a square hole). All told there are 10 of these bolts holding the camper on.