the left pic is a real simple tarp and spreaders. You can use 3/4 pvc with 1/2 emt stuffed inside ( oil it, its a tight fit) This will become your uprights and four legs as well as the spreader . Just slide the inboard legs in the reciever upright and add the spreader between them. Sewing a hem in a tarp will make a slid on pocket for the tarp to slide over the spreader. Note: if you hem about 18 to 24 inches from the end the flap will drape down between the trailer wall and the legs to help hold out wind driven rain. The two out board legs can simply fit in gromets and be staked off.
The drawing on the right is a 10x10 or 12 x12 popup gazebo room. The inboard legs can be lashed to the ladder box support or simply the trailer frame or ladder box itsself. To avoid allowing the outboard side to lift in destructive wind strap it off to any heavy coolers toolboxes or whatever.
I love my gazebo It has been everywhere In all kinds of weather. It has been the kitchen ,the livingroom, a changing room, and has even housed the porta potty in one corner.
With the mesh side walls it is even a cooler place to sleep on a stifeling hot night. The solid walls break the wind and rain and are a real asset. Nothing like 100 - 144 extra sq feet of living space when desired.
