Stopper

A stopper knot is a type of knot tied at the end of a rope to prevent the end from unraveling, or slipping through another knot. The two most common types of stopper knot are the overhand knot, where the rope is formed into a loop and the end of the rope threaded through the loop, and the figure eight knot, a more complex knot that produces a larger lump at the end of the rope.

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A stopper may also be a truncated conical piece of rubber or cork used to close off a glass tube, piece of laboratory glassware, or wine bottle. A rubber stopper is called a rubber bung by some.

Before cork came into common use, wine bottles were sealed with custom ground glass stoppers, but these were not very airtight and had the unfortunate tendency to shatter.