Figure eight

Figure eight
Other names	Figure 8, eight
Use(s)	Tying onto the rope end/middle, end-knot (single strand, marking)
Pros	Reliable, easy to inspect, low decrease of the rope strength
Cons	Tedious to untie after a lead fall in some cases, figure-eight bend is prone to rolling
Category	Knot
Strength	~60-80% in normal (non-ring) load. Differs by author, type of measurement and rope

The Figure-eight loop is the most used knot for tying-in and one of the two widely accepted knots for tying-in at the end of the rope (the second being the re-threaded bowline).

Tying

Follow-through (tie-in on the rope end)

This method is the most commonly used method for tying-in onto a rope end.

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  Take a bight of a rope and turn its one end around the other, making a full 360° turn (1)

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  Pull the rope through the upper eye (2), creating a figure-eight knot

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  Pull the rope through both eyes of a harness next to the belay loop (3)

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  Continue by following-through... (4)

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  ... the original figure-eight (5)...

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  ... knot (6)

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  Tighten the rope ends one at a time (7,8,9,10)

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  Inspect the knot and check if the loop is threaded through the harness correctly (11)

The inspection described in the last step should be also done as a part of the partner check.

On a bight (tie in in a middle)

Steps description: Take a bight of a rope and do a half-turn around itself (1,2). Then pull the bight through the loop made by the turn (3) and slightly tighten the knot (4). If the knot is malformed, dress it properly for easier checking (5) and once finished, inspect the knot (6).

Preventing from getting stuck

Figure 8 tends to get hard to untie in some cases. To prevent the issues, always dress the knot and tie the form where the load strand goes in a bigger diameter around closer to the center of the knot as illustrated below. This variant also has a slightly higher loading limit (10% difference, both variants are completely safe). As well studied and well-documented/illustrated by Hard is Easy, if the figure 8 is not dressed and tightened properly before loading it, it tends to malform substantially after taking a fall, resulting in a knot which is hard and sometimes even almost impossible to untie. Rope parameters (diameter, stiffness) also play a role. Last very important parameter discovered was if the load strand goes on the top of the knot, or in the middle of the knot.

Rolling

The Figure 8 bend knot can capsize and roll over itself already around 3 kN of force (then it snaps). For that reason it is not an ideal knot for tying two ropes together. There are speculations that the using of Figure 8 bend knot during rapelling is the reason why overhand-bend knot is known as an European Death knot in US.