b.) Common practice of a female lowering her vagina over an automobile's gear shift knob, usually done after coming home without getting laid or having a fetish for auto-erotica.
c.) The twisting of the hand around the male penis, especially over the head, as if turning a door knob, during the performance of oral sex or masturbation.
Barbara told her date that if he didn't fuck her she would ride the gear shift(knob job).
Sharon can't suck cock worth a shit; she a knob jobber.
Linda jacked me off so hard last night, I thought she would tear my knob off.