What is an iron hook of a hoisting tub, to which a tackle is affixed. Tug iron, an iron hook or button to which a tug or trace may be attached, as on the shaft of a wagon called?

tug — (Mining.) An iron hook of a hoisting tub, to which a tackle is affixed. Tug iron, an iron hook or button to which a tug or trace may be attached, as on the shaft of a wagon. (Webster's 1913.)