Which knot helps prevent the end of a line from coming unlaid?

The Double Matthew Walker knot is specifically designed to bind the end of a rope or line, effectively preventing it from fraying or becoming unlaid. This knot creates a secure, thick area at the end of the line, which helps maintain the integrity of the rope fibers. It is particularly useful in marine applications where lines can be exposed to various stresses and environmental conditions, ensuring that the rope does not unravel on its own.

In contrast, while other knots mentioned have their uses, they are not primarily intended for preventing the unlaying of a line. For example, the Double Fisherman's Knot is great for joining two lines together, the Figure Eight Knot is primarily used for creating a strong stop at the end of a line or for tying loops, and the Overhand Knot can also serve as a stopper knot but does not provide the same level of security against unlaying as the Double Matthew Walker. Therefore, the Double Matthew Walker is the most effective choice for this specific function.