Not sure who made their screens first, myself or harold1946. I give it to him since he posted first.
Made mine a few years back using sun screen from Home Depot and magnets. Used
THESE on the inside held in place with double sided tape. Used
THESE sewn into the screen. I used a DVD as a template for the pockets to hold the magnets and for the install stick. You want the magnets in the screen to float a bit which will make installation a touch easier.
Don't skimp on the magnets even with the high cost. You only need 10 on the inside and 10 on the screen to get the screen in place. The top corner magnets will make or break the project since they have to hold the screen in place when installing. I have a split windshield with five magnets on each along the outside edge and across the top. The lower half and center do not need support since the wipers will hold the screen down. I started with the smaller magnets both inside and sewn into the screen and they wouldn't hold the upper corner in place during install.
Before you install the magnets to the windshield get the poles on the magnets in the screen lined up so they will stick together when you fold the screen up. The screen material will buffer them enough so you don't have to worry about cracking them when they stick. And don't let the big magnets get anywhere near each other. They will slam together across your work bench and shatter. Get a bit a skin between them any you'll have a reminder welt for a week.
You'll need to use either a wooden dowel, something aluminum or fiberglass to install. Anything with an iron content the magnets will stick to. A $2 3' dowel works fine for me.