If you enlarge this picture, you'll see that I have a problem in the basement.  Piper likes to sit in this window.  But he can only get to it by jumping to and from the back of the chair.  The chair rotates.  Sometimes, he claws up the wall above the chair getting down.

So I built a shelf for him.  Scrap lumber, scrap carpet, leftover paint from the stairwell.

Put a smaller shelf under it, spaced for coffee mugs and sideways books.