section_path: History/Automobiles/Horizontally-opposed pistons
section_name: Horizontally-opposed pistons
paragraph_text: Horizontally-opposed pistons
  
  In 1896, Karl Benz was granted a patent for his design of the first engine with horizontally opposed pistons. His design created an engine in which the corresponding pistons move in horizontal cylinders and reach top dead center simultaneously, thus automatically balancing each other with respect to their individual momentum. Engines of this design are often referred to as “flat” or “boxer” engines due to their shape and low profile. They were used in the Volkswagen Beetle, the Citroën 2CV, some Porsche and Subaru cars, many BMW and Honda motorcycles. Opposed four- and six-cylinder engines continue to be used as a power source in small, propeller-driven aircraft.