This knot is very useful for adjusting tie downs quickly and easily. For example, a tarp could be held down by a series of these knots and be made very tight so the wind cannot make it rise, and easily be removed simply by sliding the knots later. A taut line knot is also used to keep large tents from sagging by keeping tension on the lines leading to the stakes.
I need to learn this knot!
Yes you do!