I am lucky to have the trees to attach the sails to. I was going to use eye bolts and carabiners to attach the sails to the trees, but I worried about how that may damage or stress the trees. So they are hanging on wire looped around the tree trunk.
Here you can see that the fabric is really more of a plastic screen. Rain and wind go right through.
Sewing a hem
I bought two rolls in Home Depot's garden section along with the grommets for the corners.
Grommets are labeled for easy install every spring.
Here you can make out some of the wires holding the sails to the trees