A couple mini bungee cords are used to keep the Shield in place and from blowing around in the wind. The bungee cords should be just barely taut. They will stretch a bit over time.
Attach the other end of the bungee cord to a screw eye.
I had to crimp the hooks on the bungee cord a little bit to keep them from coming free too easily, especially after they stretch. I want mine to come free for when I hang the Shield horizontally in the winter -- we want the sun then!
So I added a couple more screw eyes to the back wall which allows me to swing the shield up and out of the way in winter and when we have a storm or very windy day. You'll have to check out how you can best "store" the Shield out of the way. (Maybe you have some better ideas.)