A part of the cat tower broke off. The only type of nut I had that would fit the cat tower was a random wing nut but it was a bit sharp. One of our cats likes to rub her face on everything so we can't have something sharp exposed. This wing nut cover did the trick. Print with a support from the bed only so you can just pop the middle section out. The inside should be hollow.

If your wing nuts are larger, you will need to scale the stl file a bit.