Sluice ( SLOOS) is a word for a channel controlled at its head by a movable gate which is called a sluice gate. A sluice gate is traditionally a wood or metal barrier sliding in grooves that are set in the sides of the waterway and can be considered as a bottom opening in a wall. Sluice gates are one of the most common hydraulic structures in controlling flow rate and water level in open channels such as rivers and canals. They also could be used to measure the flow. A water channel containing a sluice gate forms a type of lock to manage the water flow and water level. It can also be an open channel which processes material, such as a River Sluice used in gold prospecting or fossicking. A mill race, leet, flume, penstock or lade is a sluice channeling water toward a water mill. The terms sluice, sluice gate, knife gate, and slide gate are used interchangeably in the water and wastewater control industry. They are also used in wastewater treatment plants and to recover minerals in mining operations, and in watermills.