1The mark in plain words
In one sentence…
Lateral marks tell you where the channel runs: in Region A, red to port; in Region B, the other way round.
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.
2See 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.
3How 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)
4Key points
- 1.
Region A: red to port returning from seaward. Region B: red to starboard.
- 2.
The region changes the colours, not the lateral logic of the channel.
- 3.
Shapes: can on one side, conical on the other.
- 4.
The chart confirms the direction of buoyage, not habit.
5Frequent 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.
6Exam keys & interpretation
Exam keys
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.
Shape saves you at night and in bad weather: can and conical stay different even when colour misleads.
7Full lesson & sources
Open the full lesson (diagrams and official references)
Lateral marks indicate the port and starboard sides of a channel or fairway in the conventional direction of buoyage.
Region A (used through Europe, Africa, most of Asia and Australia):
- Port-hand mark: red, usually can or cylindrical, red light if lit
- Starboard-hand mark: green, usually conical, green light if lit
Region B (used in the Americas, Japan, the Republic of Korea and the Philippines):
- Port-hand mark: green, usually can or cylindrical, green light if lit
- Starboard-hand mark: red, usually conical or nun, red light if lit
The essential point is the direction of buoyage. In many approaches it is from seaward toward harbour, but rivers, estuaries and local systems may define it differently on the chart.
At a channel division, a modified lateral mark identifies the preferred channel: it retains the lateral main colour and topmark, with one broad horizontal band of the opposite colour. Its light is composite group flashing Fl(2+1), in the main colour. In the conventional direction, keep the can-shaped mark to port for a preferred channel to starboard; the arrangement reverses for a preferred channel to port.
8Test your knowledge
You are returning from seaward in Region A. Which mark do you leave to port?
Keep studying…
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