A CSK one way clutch or freewheel drives in one direction but not in the other. The freewheel in a bicycle lets you pedal up hill and "freewheel" down the other side. Inclined conveyors may employ a freewheel (back stop clutch) fitted to the head shaft so that in case of transmission failure the conveyor will not run back causing damage or injury. A rowing machine in a gym will have a CSK type freewheel (over run clutch) to allow the return stroke of the "oar" without resistance. Press feeds for punching, cropping and forming often employ freewheels (indexing clutch) to provide intermittent feed. Standby drives to operate when main power fails employ freewheels or centrifugal clutches as overrun clutches.