The first step was to string a cable between the two trees. The height of the cable would be determined by the amount of slope. I didn’t know how much slope the cable would need when I started. But I wanted the rider to be near the ground when he / she finished the run. I took a best guess at how high the starting point would be to have a cable slope that let the rider go fast enough, but not too fast, and still end up near the ground. I could always adjust it later if it was too high or too low.
I attached the cable to the starting point about twenty feet up the tree. I didn’t want the cable to bite into the tree bark and eventually damage the tree, so I cut some pressure-treated 2x4s to hold the cable of the tree.