Rule 24(b) of the 72 COLREGS states that when a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit, they are regarded as a power-driven vessel and must exhibit the lights under Rule 23. A ``composite unit'' is interpreted to be a pushing vessel that is rigidly connected by mechanical means to a vessel being pushed so they react to sea and swell as one vessel. ``Mechanical means'' does not include the following:
(a) Lines.
(b) Hawsers.
(c) Wires.
(d) Chains. [CGD 76-133, 42 FR 35792, July 11, 1977. Redesignated by CGD 81-017, 46 FR 28154, May 26, 1981]