I have a horizontal gliding window that opens to my patio and I wanted to put a cat door in it so these little buggers can get out. I looked at buying one, but wow they’re expensive.

My thoughts are to build a frame out of 1x1"s and have plexiglass in between it with one of those door flaps you can buy to install into it.

Would that work? Be sufficient enough? The window is never in the sun and not exposed to a lot of elements at all, so I don’t think I need to go over the top.

And before anyone gets up in arms, the patio is netted in and the cats can’t escape. They’re not free roam, just allowed to be outside in their controlled area.