Which type of knot is used as a stopper knot to prevent rope from passing through a rescue pulley?

The figure-eight knot is utilized effectively as a stopper knot because of its ability to create a large, secure knot at the end of a rope. This knot prevents the rope from slipping through devices such as rescue pulleys, ensuring safety during rescue operations. The structure of the figure-eight provides a reliable and easy-to-identify knot, making it a common choice among firefighters and rescuers. Its shape and stability allow for easy inspection, and when tied correctly, it retains a significant amount of strength, making it suitable for high-stress situations encountered in rescue scenarios.

Other knots, while useful for other applications, do not serve this specific purpose as effectively. For example, the bowline creates a fixed loop but doesn't provide the necessary bulk to act as a stopper. The clove hitch is primarily used for securing objects and is not designed to prevent slipping through devices, while the sheet bend is generally used for joining two ropes of different diameters and does not function well as a stopper knot in this context.