Here's the cat ladder that I made for Brian's cats. The picture to the right is at his house. That's Gabe on the top and Syja on the bottom.
It's made from a four foot tall step ladder and used 500 feet of 1/4" sisal rope. The carpeted pieces are parts of a 12" diameter cardboard concrete mold that I bought at a building supply store. The round carpeted parts were the hardest by far and if I do this again, I'll just do rope. We put two by fours across the bottom to anchor it more securely.
It was a hit as a gift, even if it was almost a month late, though I'm sure the Utah catnip I rubbed into the carpet helped.
Here's the ladder being quality inspected at our house. That's Xena on the top, Gabby's on the first rung, Lissy's on the floor behind her and Lucy's looking into the tube.
I was not in favor after we took it away and they have been lobbying to get their own ladder since. The other three cat trees in the house just aren't as good.
Brian's cats / home