Along with the 2 cats, my sister donated a used cat-tree she'd picked up via Facebook. I got rid of all my plants and shoved it in the front window.
I screwed on a 3'x4" scrap of lumber to keep it from wobbling. Last summer I wrapped that in jute.
It held up until the end of winter. My second attempt has involved sisal rope, a wood glue/hot glue combo, clamps, and many, many hours. We'll see how long it lasts.