What is a figure 8 on a bight used for?

The figure 8 on a bight is primarily used to tie a closed loop in the middle of a rope, which is essential for creating an anchor or loop knot. This closed loop is advantageous in various rescue scenarios and when securing equipment, as it provides a reliable attachment point that can withstand significant loads. The knot's structure ensures that it holds firm under strain, which is critical for safety in firefighting operations. This makes it especially useful for securing harnesses, rigging systems, or anchor points when rappelling or performing high-angle rescues.

While the other options describe different knot functionalities, none convey the specific purpose of creating a strong, fixed loop in the rope that can be used for anchoring purposes as effectively as the figure 8 on a bight does.