Wrench used to hold the bell of a Cobra 2204 sized motor.
To use place the wrench on the motor such that the grooves engage the bell. Push down on the yoke of the wrench to keep it firmly engaged. Tighten or loosen the prop.
The wrench is not extremely strong and cannot take the stress to completely tighten or loosen a prop. So it's always a good idea to grab onto the prop when loosening or tightening.