diamondsilkies
Songster
Like @NFLchicks, I keep my brooder out on my porch, too, so my lid is built to keep out the cats as well as bobcats and snakes. Probably a little more heavy-duty than you'll need, but it's held up well over the years.
Here's a picture from when we were building it. It's pretty much just a thick piece of plywood with ventilation and a door cut out. You can't see in the picture, but I also made a groove in the bottom to fit the lip of the stock tank. There's a coat of polyurethane to keep it from being warped by water. Makes it easier to wipe down, too. There are two identical pieces that we sandwiched the chicken wire between.
Here's a picture from when we were building it. It's pretty much just a thick piece of plywood with ventilation and a door cut out. You can't see in the picture, but I also made a groove in the bottom to fit the lip of the stock tank. There's a coat of polyurethane to keep it from being warped by water. Makes it easier to wipe down, too. There are two identical pieces that we sandwiched the chicken wire between.