I saw this picture of a set of PB over at CF Santa Cruz. Looks like something that could be made fairly inexpensive. Somebody could probably use wooden planks instead of bars if they wanted. Rails would probably take quite a bit of work since they are a composite, I think.
If it was made a bit more robust, I could see swinging on them. In HS, our parallel bars were merely made entirely of metal ( dunno what kind really ) in basically a sand pit though we did have a porta-pit.
