Engines are always on the go once switched on, to allow for drive to be broken for change of gears and idling the transmission uses a part known as a clutch. The Clutch consists of pressure plates and friction plates with a splined middle, the splined middle is conected to the gearbox and the pressure plate and friction plate is pushed up against the engine flywheel, when the clutch is pressed the friction plate is forced away from the flywheel stoping more momentum being transfered into the gearbox. By breaking drive it allows power to be slowly applied and removed to ensure smooth and safe driving.