To practice precisions. They work really well, I can move them as far apart as I wish, and if the wood bars break (They were all we had at the time), my dad and I are going to replace them with metal bars. I want to be able to use them on the grass, because that's where they'll slide around the least, but I'd have to wait until it dried, or the wood/shoes will get wet, then something bad may happen...
Here's some pics. If y'all want, I can post the instructions on how to make them.

