Many scouts learn how to build a rope bridge. Not only is it a way to learn how to tie knots, it can also be useful to treehouse makers that want to start building a little tree villiage, with enough effort. Trestles are built using high-quality spars to provide a support system for the rope bridge, and the ends of the ropes are tied to trees on either side to maintain the tension and strength of
. the bridge. Another rope can be strung over the bridge to support someone in a harness, for safety's sake. You can find more information here: http://glenn.cockwell.com/scouting/Build%20a%20Rope%20Bridge.pdf