For the exact text concerning arcs of visibility, please see Rule 21. This guide is intended to give a graphical representation of Rule 21 (with the exception of an all-round light and flashing light).

Lighting DiagramMasthead Light Starboard SideLight Port SideLight Stern Light Towing Light Special Flasing
imagemapstbdarc towingarc mastheadarc portarc sternarc