Rule 24 - Towing and pushing
A power-driven vessel towing shows: two masthead lights in a vertical line instead of Rule 23(a)(i)/(ii) (three if the tow exceeds 200 metres from stern to the after end of the tow); sidelights; a sternlight; a towing light above the sternlight; and, if the tow exceeds 200 metres, a diamond shape. A pushing vessel rigidly connected to the vessel pushed (a composite unit) is lit as a single power-driven vessel under Rule 23. Pushing ahead or towing alongside (except composite units) shows two masthead lights, sidelights and a sternlight (no towing light). The vessel or object being towed shows sidelights, a sternlight, and, if over 200 metres, a diamond shape. Inconspicuous, partly submerged tows show white all-round lights spaced according to their breadth and length, plus a diamond shape at the aftermost end.
Rule 25 - Sailing vessels and vessels under oars
A sailing vessel underway shows sidelights and a sternlight; under 20 metres these may be combined in one lantern at the masthead. She may additionally show two all-round lights in a vertical line at the masthead, red over green (not together with the combined lantern). A sailing vessel under 7 metres shows these lights if practicable, or otherwise has an electric torch or lantern ready. A vessel under oars may show the sailing-vessel lights or keep a torch ready. A vessel under sail that is also being propelled by machinery shows a forward, apex-down conical shape.
Rule 26 - Fishing vessels
A vessel engaged in fishing, underway or at anchor, shows only the lights and shapes of this rule. Trawling: two all-round lights in a vertical line, green over white (or two cones apex to apex; a basket may replace the shape under 20 metres); a masthead light abaft of and higher than the green light (not obligatory under 50 metres); when making way, sidelights and a sternlight are added. Fishing other than trawling: two all-round lights, red over white (or the same cone shape); if gear extends more than 150 metres horizontally, a white light or cone apex-up in the gear's direction; when making way, sidelights and a sternlight are added.
Rule 27 - Vessels not under command or restricted in ability to manoeuvre
Not under command (NUC): two all-round red lights in a vertical line (or two balls); when making way, a masthead light, sidelights and a sternlight are added. Restricted in ability to manoeuvre (RAM): three all-round lights, red-white-red (or ball-diamond-ball); when making way, a masthead light, sidelights and a sternlight are added; at anchor, these lights supplement the normal anchor lights. A RAM vessel engaged in cable-laying, dredging or underwater operations, where an obstruction exists, additionally shows two red lights/balls on the obstructed side and two green lights/diamonds on the side where passing is safe. Where a diving vessel is too small to show the full set, three lights (red-white-red) plus a rigid replica of code flag "A" at least 1 metre high may be shown instead. Vessels under 12 metres (except those diving) are not required to show this rule's lights.
These two groups of lights let the Rule 18 give-way hierarchy be recognised at night.
