That was my backyard engineering challenge. The trailer is 7' wide, but I needed the stake sides (plus front and back) to fit into a 6.5' pickup bed, so I built it in two sections and attached them at alternating points with three carriage bolts and wing-nuts. They are then attached at the corners with hasps and clevis pins. Now, the dovetail presented a bit of a challenge as there were no stake pockets, but I counted on getting support from the ramps, since they'll be in the up position while using the sides, so I included them as a structural brace. The tailgate is simply wedged against the ramps, and the end result is very stiff and strong, while still easily installed or removed and disassembled. Sorry, one of the pics got a little blurry due to bumping the cellphone, but hopefully, you'll get the idea.
Joe