Adventist Youth Honors Answer Book/Knot/Taut-line hitch
From Pathfinder Wiki
Use: The Taut-Line Hitch is an adjustable loop knot for use on lines under tension. It is useful when the length of a line will need to be periodically adjusted in order to maintain tension. It is made by tying a Rolling hitch around the standing part after passing around an anchor object. Tension is maintained by sliding the hitch to adjust size of the loop, thus changing the effective length of the standing part without retying the knot. When under tension, however, the knot will grip the cord and will be difficult to cause to slip.
It is typically used for securing tent lines in outdoor activities involving camping, by arborists when climbing trees, for creating adjustable moorings in tidal areas, and to secure loads on vehicles. A versatile knot, the Taut-line hitch was even used by astronauts during STS-82, the second Space Shuttle mission to repair the Hubble Space Telescope.
How to tie: