Start with the supplied original saw-tooth wheel and single coral pawl. Keep the wheel axle, pawl pivot and camera fixed. Turn the wheel slowly counterclockwise in the drawing so the nearest sloping tooth face lifts the pawl tip around its pivot. After that tooth passes, lower the same pawl into the next valley. Attempt a very small clockwise reverse rotation; the adjacent steep tooth face meets the pawl tip and the wheel stops there. Keep the wheel and pawl rigid, distinct and at the same scale, with the pale mark attached to the wheel. No tooth passing through the pawl, extra gear, detached pivot or sustained reverse spin. End with the tip visibly engaged against the blocking face. One small advance and one blocked reverse attempt in one continuous shot.