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. A monkey's tail "is a permanent or semipermanent stopper that is put in the bight as well as the end. It is also called single throat seizing, seized round turn, clinch, and pigtail...A small round turn is first taken, and a throat seizing, in length about a quarter of the round of the clinch, is put in. The monkey's tail is preferred for the purpose just described because it does less damage to rope than any knot. When the monkey's tail fetches against the rack the seizing takes the burden." At the end of a line A stopper knot is tied at the end of a rope to prevent the end from unraveling. It then functions like a whipping knot. A stopper knot is tied at the end of a rope to prevent the end from slipping through another knot, or passing back through a hole, block, or belay/rappel device. It then functions like a leash handle. Knots commonly used for this purpose are: Overhand knot Double overhand knot Figure-eight knot Stevedore knot Ashley's stopper knot The Chinese button knot and the Celtic button knot are decorative stopper knots. Around the standing part When a stopper knot is tied outside another knot and around the standing part it can also be called a backup knot. Tying the end around the standing part helps prevent the knot from unraveling by not allowing the end to slide back into the knot: a kind of insurance against failure of the knot. Examples of this usage are often seen in climbing, rope rescue, and other safety-of-life situations. Common knots used for this purpose are: Overhand knot Double overhand knot/strangle knot Double fisherman's knot Nautical usage In nautical settings, a stopper may refer to a length of rope that is belayed at one end with the other