A plug in sanitation is an object that is used to close a drainage outlet firmly.
The insertion of a plug into a drainage outlet allows the container to be filled with water or other fluids. In contrast to caps, plugs are pressed into the hole and are not put over the hole.
Plugs are most commonly encountered in the bathroom or kitchen, for use in bathtubs, washbasins or sinks.
Typically plugs are made from a soft material, such as rubber, or have a soft outer ring, so that they can be fitted to holes slightly smaller than their diameter; this ensures a tight seal.
Some modern plugholes dispense with the need for a separate plug, having instead a built-in 'pop-up plug' operated by a handle on the sink, that can move up or down to open or close the plughole.