How to use it
1“Learning → Who gives way”.
2Your vessel — under sail, under power, under oars.
3The other vessel — sailing, power-driven, engaged in fishing, a tug, constrained by draft, restricted in ability to manoeuvre, not under command.
4Relative position — where it is: to starboard, to port, ahead, astern (overtaking), head-on, in a narrow channel.
5For sailing vessels a tack is added: starboard, port or “tack not visible”.
The diagram redraws immediately, and under it comes the conclusion: who gives way, what to do and under which rule. “Open the rule” leads to the text.
The night view
The “Show this situation at night” switch turns the diagram into what you will actually see in the dark — lights only. It is worth checking yourself: by day the answer is obvious, at night it is not.
What the builder does not do
It does not take wind, current, depths or traffic into account. A rule says who gives way, but it does not cancel the duty to keep a look-out and to manoeuvre early and decisively.