A conveyor belt or belt conveyor consists of two end pulleys, with a continuous loop of material that rotates about them. The pulleys are powered, moving the belt and the material on the belt forward. Conveyor belts are extensively used to transport industrial and agricultural materials, such as grain, coal, ores, etc. Conveyor belts with regularly spaced partitions are often called elevator belts. Conveyor belts are used in self-unloading bulk freighters and in live bottom trucks. This technology is also used in conveyor transport such as moving sidewalks or escalators, as well as on many manufacturing assembly lines. Stores often have conveyor belts at the check-out counter to move shopping items. Ski areas also use conveyor belts to transport skiers up the hill.