Dang. Pics and me are bad news. If I'm not clear to you, I am sure I am not clear to a lot of other people, too.
A fly is just an additional layer of fabric between the top of the r-dome and the sky.
It is anchored to the driver's side wheel fender to pull it tight across the top to minimize the gap with the top and side of the r-pod.
Then, the 4 corners of the fly are held tight by fastening ropes to available supports, like trees or stakes.
My 'fly' is a tarp with sail slugs that I usually use as a stand-alone awning when I don't put up the r-dome, using the pod's keder rail.
I regret very much that I'm not as clear as desired, but thanks for helping me to do a better job.