The mark in plain words
- What do they mark?The port and starboard sides of a channel or fairway, always in the conventional direction of buoyage, not according to the way you happen to be heading.
- Region A or B?In Region A the port-hand mark is red (can or cylindrical) and the starboard-hand mark green (conical). Region B swaps the colours: port green, starboard red.
- How do I know the direction?Check the chart. Many approaches run from seaward toward the harbour, but rivers, estuaries and local systems may define it differently.
- And at a channel division?A modified lateral mark shows the preferred channel: it keeps its main colour and topmark, with one broad horizontal band of the opposite colour and a Fl(2+1) light.
See it in 3D
Turn the mark to inspect its colours, shape and topmark, then switch to night to see its light.
An interactive 3D illustration is shown here. The same content is described in the rule text and key takeaways below.
How you recognise it
- Region A · port
- Red · can (cylindrical)
- Region A · starboard
- Green · conical
- Region B · port
- Green · can (cylindrical)
- Region B · starboard
- Red · conical
- Light
- Same colour as the mark
- Preferred channel
- Broad band + Fl(2+1)
Frequent mistakes
Wrong: "Red is always to port, anywhere in the world."
Right: Only in Region A. In Region B red is on the starboard side.
Wrong: "The colour is enough; the direction of buoyage doesn't matter."
Right: Without the conventional direction, the colour doesn't tell you which side to pass.
Wrong: "The horizontal band makes it a different kind of mark."
Right: It is a modified lateral mark: it shows the preferred channel at a division.
Exam keys & interpretation
- If the question doesn't name the region, look at the country: Europe and Africa are Region A; the Americas and Japan, Region B.
- Before choosing a side, check whether you are going with the conventional direction or against it.
- Fl(2+1) in the main colour = preferred channel, not a special mark.
How to read it
Think of the channel as a street with two kerbs: lateral marks show the edges, and the region only decides which colour each kerb is.
By day, shape and topmark help identify the mark; at night, use the light's colour and rhythm.
Key points
- Region A: red to port returning from seaward. Region B: red to starboard.
- The region changes the colours, not the lateral logic of the channel.
- Shapes: can on one side, conical on the other.
- The chart confirms the direction of buoyage, not habit.
Test your knowledge
You are returning from seaward in Region A. Which mark do you leave to port?