Part 2, Section C When Boats Meet at Marks and Obstructions— Mark Room
Section C contains the rules that apply when boats converge at marks and obstructions, and are intended to provide for safe and orderly transitions from one leg to the next in these tight-quartered situations. In order for that to happen, there are times when a right-of-way boat may find herself with a limit on her right of way or a temporary obligation to give roomor mark-roomto a keep-clear boat. An example is when a leeward boat is on the outside of a wind- ward boat while rounding a mark or passing an obstruction. The leeward/out- side boat may have to give that windward/inside boat mark-room to round the mark (rule 18, Mark-Room) or roomto pass the obstruction (rule 19, Room to Pass an Obstruction). Another example is when a starboard-tack or leeward boat is on the inside at a mark, and she has just tacked in the zone and she has certain obligations (rule 18.3, Passing Head to Wind in the Zone), or she must gybe to sail her proper course and she cannot sail any farther from the mark than needed to sail her proper course (rule 18.4, Gybing). Finally, there are times when a boat may need to tack to avoid hitting an obstruction, but other boats are too close for her to tack without fouling them. Rule 20 (Room to Tack at an Obstruction) gives special permission in certain circumstances that permits the boat to tack.
