At a mark, rule 18 adds a second entitlement to right of way: mark-room. Who owes it is settled at the edge of the zone, whoever has right of way.
1 · The zone
Where rule 18 switches on
Rule 18: when does mark-room start to apply as boats approach a mark?
Once one of the boats is in the zone, three hull lengths of the boat nearer the mark, rule 18 applies between boats leaving it on the same side. Hulls count, bowsprits do not.
Rule 18 applies between boats that must leave a mark on the same side once one of them is in the zone: within three hull lengths of the boat nearer the mark. Hulls count, bowsprits do not. Until then only the right-of-way rules apply, whatever anyone hails.
A mark is anything the sailing instructions tell you to leave on a stated side: a buoy, an offset mark, a committee vessel. Other classes are included; a boat for whom it is not a mark of her leg is not. Each gate mark has its own zone.
2 · Exceptions
Where there is no mark-room
Does a port-tack boat get mark-room from starboard at the windward mark?
No: on a beat rule 18 does not apply between boats on opposite tacks, so rule 10 governs even in the zone. Nor does it at a starting mark in navigable water for boats approaching to start.
Situation
Instead
Opposite tacks on a beat
Rule 10, even in the zone
Opposite tacks, only one must tack to round
Rule 10
One approaching the mark, one leaving it
Rules 10 to 12
The mark is a continuing obstruction
Rule 19
Starting mark in navigable water, boats approaching to start
Rules 10 and 11
Beat, opposite tacksport keeps clear
Approaching to startwindward keeps clear
A finishing mark is no exception: the outside boat gives mark-room there. And a mark you both leave on the same side is never a rule 19 obstruction.
3 · Who gives room
Settled when the first boat reaches the zone
Who has to give mark-room: the outside boat or the boat behind?
It is settled when the first boat reaches the zone: if they are overlapped, the outside boat gives the inside boat mark-room from then on; if one is clear ahead, the boat clear astern gives her room. Hails change nothing.
Look at the boats when the first of them reaches the zone. If they are overlapped, the outside boat must from then on give the inside boat mark-room. If not overlapped, the boat clear ahead when she reaches the zone gets mark-room from the boat clear astern.
Overlapped at the zoneoutside gives room
Clear ahead at the zoneastern gives room
The duty stays even if the overlap is later broken or a new one begins: an overlap gained inside the zone is too late. Right of way, size and hails change nothing: rule 18 needs no hail. Opposite-tack boats count as overlapped whenever rule 18 applies between them, as on a run. The outside boat gives room to every boat overlapped inside her.
If there is reasonable doubt that an overlap was obtained or broken in time, presume it was not. And no room is owed for an inside overlap gained from clear astern, or by tacking to windward, if the outside boat has been unable to give it ever since it began.
4 · Mark-room
Room to round, not room to win
Does mark-room let the inside boat swing wide for a tactical rounding?
No: mark-room is room to sail to the mark, round it on the required side and leave it astern, manoeuvring in a seamanlike way. An inside boat that must keep clear and swings wide has to keep clear again.
Mark-room is room to sail to the mark when your proper course is to sail close to it, then to round or pass it on the required side until it is left astern, a gybe at a gybe mark included. Room is the space needed in the existing conditions, current included, to manoeuvre promptly in a seamanlike way without touching the mark.
Inside but keeping clear, mark-room is all you have: swing wide for a tactical rounding and you must keep clear again. Inside with right of way, round as you like, giving room to keep clear when you change course (rule 16.1). The old clause on room to tack was removed in 2025.
5 · Tacking in the zone
Coming in on port at a windward mark
Rule 18.3: can I tack in the zone at a windward mark left to port?
Yes, but under rule 18.3 you must not then make a boat fetching the mark sail above close-hauled to avoid contact, and you give her mark-room if she becomes overlapped inside you.
At a mark left to port, rule 18.3 covers a boat that passes head to wind in the zone and is then on the same tack as a boat fetching the mark. Rule 18.2 is off between them, even if the other boat tacked in the zone too. The boat that tacked must not make the other sail above close-hauled to avoid contact, and gives her mark-room if she becomes overlapped inside.
Tacking in the zone is not forbidden: tack clear ahead and nobody is troubled. While still turning you keep clear under rule 13. Passing head to wind before the zone, or at a mark left to starboard, is outside 18.3.
6 · Gybing at the mark
No sailing on past a leeward mark
At a leeward mark, can the inside right-of-way boat sail on past it before gybing?
No farther than her proper course needs: rule 18.4 makes an inside, overlapped right-of-way boat that must gybe at the mark sail no farther from it than that course requires. The rule is off at a gate mark.
Rule 18.4 limits a boat that is overlapped inside, has right of way and must gybe at the mark to sail her proper course. Until she gybes she sails no farther from the mark than that course needs; in 25 knots a later, safer gybe may be it. An inside boat that keeps clear or need not gybe is not bound, and the rule is off at a gate mark.
7 · Ending and exoneration
When rule 18 lets go
If I break a rule while taking my mark-room, am I exonerated?
Yes, for breaking rules 10, 11, 13 or 16 against the boat owing it: within your mark-room you are exonerated under rule 43.1(b). Contact without damage is exonerated too; avoidable contact with damage breaks rule 14.
Rule 18 ends between two boats once mark-room has been given: the leeward boat may luff again, and nothing is owed back. The entitlement also ends if the entitled boat passes head to wind or leaves the zone; if they are then overlapped at the mark, the outside one gives room.
Within your mark-room
Result
You break rule 10, 11, 13 or 16 against the boat owing room
Exonerated: 43.1(b)
She squeezes you onto the mark
Exonerated; she broke 18.2
Contact, no damage or injury
Exonerated: 43.1(c)
Avoidable contact with damage
You broke rule 14
Room was enough, you hit the mark
Rule 31: one turn
Rule
Mark-room is not right of way: the right-of-way boat often owes it.
Practice questions
Questions from this topic, as the app asks them. Open one to see the answer.
Wing mark of a trapezoid course, 8 knots, both of you on port tack on a beam reach. Blue is overlapped inside you (closer to the mark) and the bow of your Melges 24 has just crossed the three-length circle; Blue's bow is still a metre outside it. Blue hails for mark-room. Does rule 18 apply between you yet?
No — rule 18 applies only once the inside boat is in the zone
Yes — rule 18 applies as soon as at least one of the two boats is in the zone, and you are
No — rule 18 applies only when both boats are inside the zone
Yes — but only because Blue hailed; without a hail rule 18 starts at two lengths
Show the answer
B. Yes — rule 18 applies as soon as at least one of the two boats is in the zone, and you are
Rule 18.1(a): rule 18 applies between boats required to leave the mark on the same side when at least one of them is in the zone.
Wednesday club race, windward mark to be left to port. You are close-hauled on port tack, one hull length from the mark and inside Red, who is close-hauled on starboard tack and fetching it. You hail "Room at the mark!" Does Red have to give you mark-room?
No — rule 18 does not apply between boats on opposite tacks on a beat; you must keep clear of Red under rule 10
No — but only because you hailed too late; a hail before the zone would have secured the room
Yes — you are the inside boat in the zone, so Red must give you mark-room under rule 18.2
Yes — the boat nearer the mark is entitled to room whatever her tack
Show the answer
A. No — rule 18 does not apply between boats on opposite tacks on a beat; you must keep clear of Red under rule 10
Rule 18.1(a)(1): rule 18 does not apply between boats on opposite tacks on a beat to windward; rule 10 governs.
Leeward mark to be left to port, 15 knots. You are running on port tack and Red is running on starboard tack; your bows are level, Red is inside (closer to the mark) and you both enter the zone together. Red hails for room. Are you overlapped for the purposes of rule 18, and who gives room?
Yes — the terms overlap and clear astern apply to boats on opposite tacks when rule 18 applies, and on a run it does; you give Red mark-room
No — you are on opposite tacks at a mark, so rule 18.1 switches off as it does on a beat
No — boats on opposite tacks are never overlapped, so rule 18 cannot apply and only rule 10 decides
Yes — but as the inside boat Red must still keep clear of you because you are to windward
Show the answer
A. Yes — the terms overlap and clear astern apply to boats on opposite tacks when rule 18 applies, and on a run it does; you give Red mark-room
Definition Overlap: boats on opposite tacks are overlapped when rule 18 applies; 18.1 excludes opposite tacks only on a beat, so 18.2(a)(1) applies.
Gybe mark of a triangle, Saronic Gulf, 18 knots. You and Grey are broad reaching on starboard tack, overlapped as the first of you reaches the zone, the mark to be left to port; Grey is inside and to leeward. Just at the mark Grey starts her gybe and you, outside, hold on so close that she has to delay it and sail past the mark. You say she had room to pass the mark and could gybe later. Who is right?
You — mark-room is only room to pass the mark without touching it; the gybe is her own business
Grey — mark-room includes the room to round the mark as needed to sail the course, and at a gybe mark that includes the gybe
Grey — but only because she is to leeward; a windward inside boat gets no room to gybe
You — a boat entitled to mark-room must sail past the mark first and gybe only when she is clear of the outside boat
Show the answer
B. Grey — mark-room includes the room to round the mark as needed to sail the course, and at a gybe mark that includes the gybe
Definition Mark-Room: room to round or pass the mark on the required side; at a gybe mark the rounding includes the gybe (rule 18.2(a)(1)).
Windward mark to be left to port, club championship. You are close-hauled on starboard tack, fetching the mark, and have been on starboard since well before the zone. Yellow, on port, tacks inside the zone right under your bow; her tack is complete, but to avoid her transom you have to luff above close-hauled for a few seconds. Did Yellow break a rule?
Yes — having passed head to wind in the zone she must not cause you to sail above close-hauled to avoid contact (rule 18.3(a))
Yes — she broke rule 13, because a boat may not tack at all inside the zone of a windward mark
No — once her tack was complete she was the leeward boat and you, to windward, simply had to keep clear
No — a boat that completes her tack clear ahead has right of way, and luffing briefly is no hardship
Show the answer
A. Yes — having passed head to wind in the zone she must not cause you to sail above close-hauled to avoid contact (rule 18.3(a))
Rule 18.3(a): a boat that passes head to wind in the zone must not cause a boat on starboard since entering it to sail above close-hauled to avoid contact.
Leeward mark to be left to port, 12 knots. You are running on starboard tack and Grey, on port, is overlapped outside you as you reach the zone, so you have both right of way and mark-room. To round for the beat you must gybe. You sail on past the mark for two lengths before gybing, to get a better angle, holding Grey out wide. She protests. Who is right?
You — you had right of way under rule 10 and mark-room, so Grey had to keep clear of whatever rounding you chose
Grey — as the inside right-of-way boat that must gybe at the mark to sail her proper course, you may not sail farther from the mark than needed until you gybe (18.4)
Grey — because a starboard-tack boat must gybe before she enters the zone
You — a boat entitled to mark-room may sail a tactical wide-and-tight rounding
Show the answer
B. Grey — as the inside right-of-way boat that must gybe at the mark to sail her proper course, you may not sail farther from the mark than needed until you gybe (18.4)
Rule 18.4: an inside overlapped right-of-way boat that must gybe at the mark sails no farther from it than needed for her proper course until she gybes.
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