This one’s pretty straightforward, really. Just your average zipline- find two secure things, and run a line between them. This is best done with a steel cable- I happen to have one lying around from an old winch. You can use a ratchet tie down and some U-bolts to tension it up. The runner is a standard pulley, and handles are just wooden dowels secured to the axle. This one is so close to the ground that we felt ok skipping the safety harness part (though we did add some foam to the ends so nobody gets bonked in the eyeball). Also, the initial departure from the ladder has a big pile of leaves under it.
I’m going to file this creatively under “5 minutes 5 bucks”- if you can’t tell, that’s open to interpretation, I’m going to assume you have these things lying around and work really fast!