CABLE-TOW:
A word not generally defined in dictionaries but which may be interpreted as a “tow-line”. The length of a cable-tow, the distance within which a freemason is required to obey a summons to his lodge, is sometimes stated to be three miles although different versions of the Old Charges gave it as five or as much as fifty miles.
With modern means of communication and travel at his command, the present-day freemason can stretch very considerably the length of his cable-tow. Various symbolic meanings have been accorded to the piece of rope with which the initiate quickly becomes familiar; perhaps the most readily acceptable is that of unity.
From “A REFERENCE BOOK FOR FREEMASONS – Frederick Smyth