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.
I’ve seen plenty of people who did the plywood thing, works fine. Weather stripping is recommended if you have lots of bugs (or are otherwise bothered by any intrusions).
If you want to see out that portion of the window, I recommend still using a plywood frame for where the door is, and plexiglass above it.