Watt's linkage (also known as the parallel linkage) is a type of mechanical linkage invented by James Watt (19 January 1736 – 25 August 1819) in which the central moving point of the linkage is constrained to travel on an approximation to a straight line. Its applications include doubling the power of a piston engine by allowing two pistons to connect to a single beam, and, in automobile suspensions, allowing the axle of a vehicle to travel vertically while preventing sideways motion.