Dave, I explained this in previous posts, but it will be easier for me to cover this again, rather than you having to search for those posts.
The material that I drape over the roof is one piece and that same piece also drapes over two sides. The weight of the material is pretty substantial but won't stay in place with winds. I used light aluminum wire (you could use twine, monofilament, or any thin wire) to hold this large panel of material down. I secured one end of the wire with a screw at the base of one side, pulled it over the roof, down the other side, and secured it with a screw. So both ends are secured with screws at the base of the sides. I did the same every 3-4'. You would then have secured this large panel with 4-5 strands of wire or other tie-down material. The material is flexible enough that roof vent(s) can still be raised. I only have one large roof vent (manual) and it raises quite easily.
I used the same technique to hold down the material going down the sides as well, and used three strands for each side. This is perhaps "over-kill", but I did not want the material to billow up in winds and wanted it close to the polycarbonate. Using the wire was far easier than having to use so many screws along the periphery of the solar blanket material. Also, with the wire, all the material can be quickly removed if I find the need to remove it when the weather is warm. I don't yet know whether that will be necessary or not. I don't think Karen ever removes her's.
For my two sliding doors, I cut out the material to fit each of the two panels. Because of the way the doors slide in, I attached the solar blanket material to the inside of the two doors with the same screws that secures the polycarbonate to the metal frame. Since my double doors face the north, I also cut a large enough piece of the solar material to cover that opening. I then attached Velcro above the door opening, one strap on each side. Now I can roll up the solar blanket during mild weather, securing it with Velcro and can release it to fall over the doors during windy cold weather. I have two pieces of that aluminum wire that crosses near the bottom and about 1/3 up to keep the flap in its place during high winds.
The solar blanket material is very easy to cut, but at 16 mil, it is durable enough to screw down, using washers to increase the surface area between screw and material.
