I just got through making one for my furkids. Although it is not finished, as it still has to be carpeted and wound with rope. But some of my cats appear to like to sleep in it. The verticals are 2- 2x4s' held together by dry-wall screws, with a lower shelf about half way up and then a top shelf that is up about 9ft.(3 meters) from the floor. There are 3 horizontal wooden bars, about 12 inches (apx, 4.8 cm) apart that facilitate my furkids ascent to the top. It is fastened to the wall by means of the top shelf, and placed in a portion of the room where I can watch them play on it. They all have taken turns trying it out at sundry times. But there are only 2 of them that like to sleep on it, namely; Amy, and Cookie. Amy is the only one who uses it all the time.

........wayne