This is what I did when we had to separate a chicken for a few days, due to flock behaviors, not disease. In other words, we wanted the chickens to still be able to see each other - I planned on fencing off an inside corner of the coop, so I screwed in a vertical line of ceiling hooks (cheaper than cup hooks) on each of the two walls I'd be attaching the garden fencing to. I measured the sides and cut the garden fencing to form an L shape, then reinforced the bottom edges by stapling on wood pieces. (Made a sturdy frame). I added a horizontal row of ceiling hooks along the upper back wall where I'd be attaching a piece of fencing for the pen top to flip open. (If you have to work around wall studs, a piece of wood can be nailed to the back wall first to make a flat surface for the hooks.) Also framed the cover by stapling thin wood trim around the edges to strengthen it, but first turned down the front edge to be secure when closed. So the top flips open easily for all the chicken's needs. You can add a hook up high on the back wall so you can temporarily fasten open (with a wire) the top if you have to reach in and get the chicken out. I made our holding pens about 2' x 3' in two corners of our coop, and they can be quickly assembled or dismantled as needed, so when they aren't needed, we're not losing that floor space. Hope this cheepie idea helps someone.