Boom preventer:
A common setup that sailors are familiar with is called a preventer. It is a line that is tied to the boom to keep it from swinging. Usually it is done on both sides so that it can be released and allow the boat to cross the wind before it is tied on the opposite side.
With RopeTies on eiter side, tying and tensioning the line is easy even with heavy resistance from weather or motion. Also when it is time to release there is no waiting, and no danger of jamming.

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All you need is two 30ft lines and two RopeTies.