Figure of 8 Belaying Device

Sometimes just called "eight", this device is most commonly used as a descender, but may also be used as a belay device in the absence of more appropriate equipment, although it does not provide enough holding power for this to be recommended.

It is an aluminium (or occasionally steel) "8" shaped device, but comes in several varieties. Its main advantage is efficient heat dissipation. A square eight, used in rescue applications, is better for rappelling than the traditional 8.

Figure eights allow fast but controlled descent on a rope. They are easy to set up and are effective in dissipating the heat caused by friction but have a tendency to put a twist in the rope. Holding the brake hand off to the side twists the rope, whereas holding the brake hand straight down, parallel to the body, allows a controlled descent without twisting the rope. 

An 8 descender can wear a rope quicker than a tube style belay/rappel device because of the many bends it puts into the rope. Many sport climbers also avoid them because of the extra bulk an 8 puts on the rack. However, many ice climbers prefer to use the 8, because it is much easier to thread with stiff or frozen rope.

Knots: Figure-of-Eight

The figure-eight knot is a type of knot. It is very important in both sailing and rock climbing as a method of stopping ropes from running out of retaining devices. Unlike the overhand knot, which will bind iron-hard under strain, often requiring the rope to be cut, the figure of eight can be easily untied after even the greatest strain.

Different types of figure-eight knots

Double figure-eight knot

Double figure-eight knot (figure-eight loop) is used like an overhand loop knot. This type of knot can be used in prusik climbing when used in conjunction with a climbing harness, a climbing rope, and locking carabiner designed for climbing, to ascend or descend with minimal equipment and effort.

Figure-eight splice knot


Figure-eight splice knot is used to quickly and effectively "splice" together two ropes, not necessarily of equal diameter. This knot is tied starting with a loose figure eight knot on one rope (the larger-diameter one if unequal), and threading of the other rope's running end through the first figure eight, starting at the first figure-eight's running end and paralleling the path of the first rope through the figure eight until the second's ropes running end lies parallel against first's standing end. The result is two figure-eight knots, each partly inside the other and tightening its hold on the other when they are pulled in opposite directions. This can be a permanent or temporary splice. While it precludes the ropes' slipping relative to each other, it is a typical knot in having less strength than the straight ropes.


Tying

• When used as a stopper knot, the figure eight takes a more compact tightened form.
• Make a bight in a rope
• Twist it around half a turn away from the working end
• Bring the working end around from below, then through the loop from above
• Pull

or like how we remember;

• Make an alien (create a loop).
• Choke it (wrap one end around the alien's "neck").
• Poke it in the eye (push the end through the "alien" loop).

 Among other uses, it's very popular as a "tie in" for attaching the climbing rope to your harness.