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.
Everything I make: LanceMakes.comThis 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 :)