As I just wrote to Dave, after you open up your 270 degrees of fabric coverage, there is a cinch strap that has to be connected from the end forward. This means that you need something sturdy and approximately Foxwing-height to tie off the strap on and pull the awning tight. On a vehicle, you could use, say, a roof rack tube on the opposite side of the awning. But based on having had Dave's Horizon for a while, I couldn't think what there was that was tall enough, far enough forward and sturdy enough to connect to this strap on a Horizon/Chaser-type trailer.
My rig's not here or I'd take a picture. If someone has a picture of a deployed Foxwing . . . well, worth a thousand words, I suspect.