INT 1 · P 20.1
Leading lights and line
LightsCore
Two charted lights and a bearing define a precise visual line through safe water.
What it means
Front and rear lights lie on the charted leading line. When approaching them, keeping the rear light vertically above the front light keeps the vessel on that line.Rhythm notation such as Fl(2) 10s is decoded in the Light rhythms guide.
Why it matters
If the lights open, manoeuvre to close them again while checking the chart and surrounding traffic. Avoid a universal 'steer toward the upper light' mnemonic—it reverses with geometry and direction of travel.