Case Q&A 2026.003

Mark-Room is room for a boat

• (a) to sail to the mark when her proper course is to sail close to it,
• (b) to round or pass the mark on the required side, and
• (c) to leave it astern.

When does a boat leave a mark astern?

A boat leaves a mark astern when the mark is behind a line abeam from the aftermost point of her hull and equipment in normal position.

In which of the diagrams below has Grey left the mark astern in position 3?

Grey has left the mark astern in position 3 in all these diagrams.

If a boat entitled to mark-room and in the zone momentarily leaves the mark astern while she is manoeuvring in the zone, is she still entitled to mark-room?

If a boat is entitled to mark-room and momentarily leaves the mark astern while she is manoeuvring in the zone, she is still entitled to mark-room if her proper course is still to sail close to the mark, or if she has not yet rounded or passed the mark on the required side.

When a boat is required to give another mark-room at a finishing mark, does her obligation include ‘room to leave the mark astern’?

Yes. At a finishing mark, mark-room also includes room to leave the mark astern.