Abstract: A self-locking cable trolley having a body member which guidingly receives a cable on which the body member rides and a length of working line that permits control of the body member on the cable. Disposed on the body member is a lock device which grips the supporting cable when the working line is manipulated in a predetermined manner so as to cooperate with a control surface also provided on the body member and swing the lock device into engagement with the cable in order to selectively retain the body member of the trolley at a desired location on the cable.