The Rules Guy: Mark Room at a Gybe Mark

Jan 19, 2022

Mark rounding is a lot like the weather. It is genuinely complex, and it causes no end of trouble, particularly for those not paying attention. Rule 18, “Mark-Room”, takes as much space in the rulebook as Rules 10 to 17. There are a few slightly more complicated situations that I would like to discuss, but this month we will start with some of the basics.

Before we dive in, note that mark rounding has so many possible variations that the rule makers have thus far struggled tin vain to make it simple. World Sailing currently has a working party hoping again to simplify this rule for the 2025-2028 rulebook.
















In the diagram, we see Blue and Yellow coming down the first reach of a triangular course, approaching the gybe mark. The first part of the applicable rule,18.1, explains when the rest of rule 18 applies: this is a mark; both boats have to pass it to port; and none of the exceptions apply, so rule 18 applies. When Yellow gets to edge of the imaginary three-hull-length circle around the mark, also known as the zone, Blue is overlapped with Yellow. Rule 18.2(b) says that when the boats are overlapped, Yellow is required to give mark-room to Blue, even if the situation between them changes later. At position 1, Blue hailed “Mark-Room”. This hail is not required but it helps both boats to understand what is going to happen.
















The second diagram is similar. Red and Green are approaching the gybe mark on the first reach. Red is not overlapped on Green. According to the same rule, 18.2(b), Green who is clear ahead, is entitled to mark-room. Green hails “No overlap. No Room. This hail is also not required, but again makes it clear to both boats what is going happen.

In the third diagram, Purple and Orange are approaching the same mark. Orange is clear ahead of Purple, so as we saw before, Purple is not entitled to mark-room. This time though, Purple gains an overlap inside the zone and despite Orange’s entitlement to mark-room, decides to continue inside Orange. The definition of mark-room includes room to sail to the mark. At position 4 and 5, Orange must stay up to avoid colliding with Purple and is unable to sail to the mark, so Purple has not given her mark-room, and thus, Purple has broken rule 18.2(b). At position 5, Orange hails “protest” and Purple would be well advised to take a penalty soon after the mark. If Orange files the protest and Purple has not taken a penalty, Purple will be disqualified.


Mark-Room Room for a boat to leave a mark on the required side. Also,

(a) room to sail to the mark when her proper course is to sail close to it, and

(b) room to round or pass the mark as necessary to sail the course without touching the mark.

However, mark-room for a boat does not include room to tack unless she is overlapped inside and to windward of the boat required to give mark-room and she would be fetching the mark after her tack.

Zone The area around a mark within a distance of three hull lengths of the boat nearer to it. A boat is in the zone when any part of her hull is in the zone.


18.1 When Rule 18 Applies

Rule 18 applies between boats when they are required to leave a mark on the same side and at least one of them is in the zone.

However, it does not apply

(a) between boats on opposite tacks on a beat to windward,

(b) between boats on opposite tacks when the proper course at the mark for one but not both of them is to tack,

(c) between a boat approaching a mark and one leaving it, or

(d) if the mark is a continuing obstruction, in which case rule 19 applies.

Rule 18 no longer applies between boats when mark-room has been given.

18.2 Giving Mark-Room

(a) When boats are overlapped the outside boat shall give the inside boat mark-room, unless rule 18.2(b) applies.

(b) If boats are overlapped when the first of them reaches the zone, the outside boat at that moment shall thereafter give the inside boat mark-room. If a boat is clear ahead when she reaches the zone, the boat clear astern at that moment shall thereafter give her mark-room.


Andrew Alberti 400Andrew Alberti is an International Judge and National Umpire. He is a member of the Sail Canada Rules and Appeals Committees. Send your questions to Andrew at







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