Closure part for a barrel (glass, rubber, wood, ceramic, plastic, silicone) that is inserted into the bunghole. To allow gas to escape or ventilation, the bung can also be inserted loosely or it has a corresponding device (valve) that only allows this in one direction. This is also called a fermentation bung (see fermentation bung). In this case, the barrel is stored so that the bunghole is at the top. If you want to ensure that no ventilation can take place during the barrel expansion, then the barrel is turned so that the bunghole (in this case firmly closed) is below the liquid level. This position is called "two o'clock" (2 o'clock position). The advantage is that the empty space formed by the evaporation forms on the smooth inner wall of the barrel. On the other hand, a "12 o'clock position" can lead to leaks, especially in wooden cones, because these can dry out in the air bubble. This poses the risk of oxidation and also large-scale shrinkage.