§ 2012. Sailing vessels (Rule 12)
(a)
Keeping out of the way
When two sailing vessels are approaching one another, so as to involve risk of collision, one of them shall keep out of the way of the other as follows:
(i)
when each has the wind on a different side, the vessel which has the wind on the port side shall keep out of the way of the other;
(b)
Windward side
For the purpose of this Rule the windward side shall be deemed to be the side opposite to that on which the mainsail is carried or, in the case of a square-rigged vessel, the side opposite to that on which the largest fore-and-aft sail is carried.