Abstract: A safety mechanism used in connection with a tarpaulin which selectively covers and uncovers a vehicle body includes a transmitting member for causing the tarpaulin to move. A drive sprocket is connected to the transmitting member and is rotated by a crank handle mounted coaxially on the drive sprocket shaft. A forward motion pawl resiliently engages a ratchet on the shaft to assure one way operation when the handle is in its operative condition. A safety pawl is selectively moveable into engagement with the drive sprocket for preventing any inadvertent rotation of the drive sprocket.