The flanged, heavy steel casting at the extreme end of a drawbar or draft gear assembly. It houses the knuckle and locking pins in an automatic coupler, taking the direct impact of buffing forces when cars come together. Car knockers inspect this casting closely for stress cracks, as a structural failure here will drop the entire coupler assembly directly onto the rails.
Heard on the job
The knuckle is fine but the drawhead itself has a massive crack right down the side casting.