Oh I highly recommend PVC pipe. The thin-wall 3-4" stuff is great. I got a 10 foot length from my local (pet friendly) hardware store (I've taken in my dog, both our Beardies, and a rat or 2 on occasion) for about $7 !!! That, a hacksaw, a little sandpaper (to smoothe off the edges), and a 3/8" drill; a couple of cheapie carabiners and you have a washable, comfy, climby thing. I even will put them at an angle and use them as ramps. The inside has a slight brushed finish so little ratty-feet can walk up so long as it isn't toooo steep. OH- and I tend to hang them at a very slight tilt, pointed away from anything damageable. PVC isn't so much absorbent (like cardboard) and I had a drainage incident - of course right into a food bowl. sigh.
At least I'm trainable. :lol: