A diagram of the grasshopper escapement invented by British clockmaker John Harrison in 1722. An escapement is a mechanical linkage in a clock that gives the clock's pendulum periodic pushes to keep it swinging, and releases the clock's gear train to advance a fixed amount each swing, moving the hands forward at a steady rate. The grasshopper was an unusual low friction escapement that was used in a few clocks made by Harrison and the Vuillamy brothers, but did not see wide use.