We made a screen cover for our Boler
door. And kept it as simple and inexpensive (read cheap) as possible. I bought a piece of screening from the hardware store and cut it larger than the door opening. I then used self sticking Velcro above the door opening on the inside and stapled the other Velcro strip along the top of the screening material. I also put a few smaller pieces of Velcro along the side. I weighted it down by pinning large, thin washers to the bottom. The screening hangs below the door opening. When we want to use it, I just stick it in place. With no zippers to access, I can push it aside to get in and out. I live in Alberta, and if we are camping in cooler weather, it isn't needed as the bugs don't like cold. If it is too windy, bugs aren't a worry either. The Velcro has stuck in place now for three years through -40C and +40C. Worse case scenario, is I have to replace the inside Velcro strips every now and again, but so far not. It doesn't look pretty, but it works. And no need to build a frame to fit it. The odd bug gets in, but that would happen anyway as one goes in and out of any type of screen door. That's what the bug swatter is for!