I built framed screens for all of my windows when I built my blind,and used magnetic tape on the screen frames to stick to the sheet metal that I use around my window openings.
I bought everything to do it at Home Depot or Lowes.
I originally used a thick black fiberglass screen material for the screens since I didn't bow hunt out of my blind.
The window opening on the left doesn't have a screen on it,but the right window opening does. You can see how much difference the screen makes on a sunny day.
This year I was able to bow hunt with my crossbow in the blind so I needed to use something that I could shoot thru.I found some sheer camouflage fabric on Ebay and bought a couple yards of it.
I really like this stuff,it blocks the sunshine pretty good,and you can see thru it. For completely blocking out any light on my side or back windows,I just hang up some dark brown hand towels that I bought for just that purpose.