One of the sling beds in the catio gave up under the weight of the kitten and popped its grommet. I removed the rest, it has lasted awhile, and puzzled over a replacement. The two sections of 1 x4” wood that I screwed to the catio supports seemed about the size of a pillow case. It turned out it was a little wider, but with a quick seam and a couple of snipped holes, I converted an old pillow case into a cat sling bed that slides over two parallel boards.

Cotton does degrade in the sun, but this might be a better design idea than grommets in the corners screwed to the board. I’ll see of the cats use this setup, and if they do, replace the cotton with outdoor resistant fabric.