What is the Figure 8 knot commonly used for?

The Figure 8 knot is primarily used to create a secure loop at the end of a line. This characteristic makes it particularly useful in various contexts, such as climbing, sailing, and other applications where a strong, reliable loop is necessary. The knot is easy to tie and untie, even after bearing heavy loads, which is critical for safety and functionality in many maritime activities.

While the other options may reference uses for different types of knots, the specific design and functionality of the Figure 8 knot do not align with these purposes. For instance, to secure two lines together, knots like the square knot or the double fisherman's knot would be more appropriate. Similarly, preventing a line from passing through a sheave typically involves other knotted techniques or configurations. While a Figure 8 can indeed serve various roles, its primary intent aligns with creating a loop at the end of a line, making it an excellent choice for situations requiring a reliable end attachment.