I use the "T" & "Y" shaped 4" or 5" white PVC pipe from Lowe's for my chins to play on, hide in ... some even prefer to sleep in them. It's a must with me for kits when the daddy is allowed go back in the cage after the 10 day waiting period after mom delivers. We also get the pipes that size (4" diameter) and cut them into 6" to 12" sections. These are easily washed and/or sterilized in the dishwasher (top part only). Some of mine have even learned to walk on the top of the pieces of pipe to get them to the feeding bowl.
I tried to find the pictures of the PVC play pipes made for chins, but could not find it ... I'll keep looking. PVC pipe is a form of plastic, but it does not come off in pieces, when chewed, like most plastic. PVC comes off in a powder form that falls to the bottom of the cage.
I'll try to describe the play bars ... picture a flat square made from 1 inch diameter PVC pipe, joined together by 45 degree connecting pieces. Now picture 1, 2, or 3 bars (different height's) attached to this base like an upside down U ... using "T" connections to the base to secure them in place. The top of the pipe (the bottom part of the U) would be wrapped with twine or rope to give a strong footing for the chin. They will play on these for hours, once they figure them out.
Other parts of the play ground can be made from boxes (make sure there are no metal staples left in the boxes), with holes and doors cut out of them.
Jo Ann