If you enjoy this project, then I encourage you to buy my book, Rubber Band Engineer. It's full of more awesome and original projects crafted from household hardware. You can find it wherever books are sold.This structure allows you to set up a slackline without using trees, poles, or A-frames. It's very easy to build!
I suggest reading through this Instructable for ideas and then making improvements wherever you see fit. I'm definitely not a pro :)