A stopper knot (or simply stopper) is a knot that creates a fixed thicker point on an otherwise-uniform thickness rope for the purpose of preventing the rope, at that point, from slipping through a narrow passage, such as a hole in a block. To pass a rope through a block, or hole, is to reeve it. To pull it out is to unreeve it. Stopper knots prevent the rope from unreeving on its own. "Stopper" has three distinct meanings in the context of knotting and cordage. A decorative stopper knot may be referred to as a lanyard knot. — The Ashley Book of Knots