How do I temporarily screen in my garage door opening so the cat can't slip out?

I did basicly the same project last spring for my own escape artist and the setup that survived is a stapled panel, not loose netting. Loose mesh across a 16 foot opening is going to sag and bag out in a week no matter how you tension it, so I framed mine instead. Two horizontal rails of 1x2 furring strip, one up near the header and one at the floor, vertical furring strips in between every couple feet, then staple fiberglass screen or vinyl-coated hardware cloth to the whole frame. Staple through a second thin strip on top of the first so the mesh is pinched between wood, that way she can't claw it loose at any single staple. Hardware cloth is the better choice if she's a pawer, the fiberglass stuff will look like confetti after one determined session, though the vinyl-coated kind is heavier and costs more. It's rigid enugh that a cat just kind of bounces off it and moves on, and it doesn't sag beacuse the frame carries the load, not the mesh. For the no-drilling part, I screwed cup hooks into the wood header trim above the door, which most garages have, and hung the panel from those with a few eye screws and clips so it lifts off in ten seconds. The bottom sits loose on the floor with a couple of sandbags or bricks to stop her nosing under. When the mower needs through, unclip one side, swing the panel back like a hinged door, wheel through, clip it back. If there's no trim to hook into, you can stand the whole thing up freestanding with a couple of angle braces at the floor, but clipped is sturdier against a cat who likes to test things. One tip, make it about head height rather than floor to header if your tracks allow it, cats think in terms of gaps and a partial barrier they can see over seems to bother them less than a full wall, at least mine stopped staring at it after two days.

Reading this because my cat also treats the garage like her personal sunroom and I never thougt about just covering part of the opening instead of the whole thing. The idea of making it only as tall as my chest actually sounds way less annoying to build too. My worry is the sides though. Mine is skinny and once squeezed through a gap I swore was way too small for her. Did you leave any space at the edges of your panel, or does it need to go wall to wall so they can't slip around it? Also curious if the cat ever tried climbing it like a ladder, that's her usual move with anything mesh.

Second panel idea that made my setup easier to live with: build it as two halves that meet in the middle instead of one big swing-out. Mine are each about 4 feet wide, so moving the mower means opening one side instead of swinging a whole 16 foot leaf around. I put a barrel bolt on each panel where they meet so a push from the cat nose side doesn't slide them apart. If your opening is on a slope like mine, check the bottom rails sit level because mine rocked til I shimmed one foot.

Did this same dance about 20 years ago with a tomcat who thought the driveway was his territory. One thing I learned the hard way: cats climb mesh. Mine went up the hardware cloth like a ladder the first week. Fix back then was the old fence trick, angle a strip of slick panel or plastic sheet outward at the top so there is nothing to get a grip on past chest height. Worked like a charm. Also, if your tracks have the room, only run the door up about knee high and your barrier gets a whole lot smaller and cheaper to build.

Update: I went the framed panel route like you described, two 1x2 rails with mesh stapled on, and it holds taut across the opening way better than the loose stuff I first pictured. Problem now is exactly what the tomcat guy said. She climbs it. So for the angled slick strip at the top, what did you attach it to and how did it stay put?