It is an instrument to measure time that was traditionally used for the distribution of water-rights. It is made of two copper or bronze cups; the smaller one has a hole in the bottom to let the water pour through into the second cup. When this vessel is placed in a bucket of water it slowly sinks until it is completely submerged.

The time it takes for the device to fill and sink (approximately 45 minutes, however the duration may differ from qçar to qçar) corresponds to the quantity of water that flows from a basin or a stream for irrigation. This time unit of water-share is named kharouba.