On a starting line between a race committee boat and a buoy, the entire
race committee boat is a mark even though the actual end of the line is marked by a flag or some other specific point on the boat. Note that anything that is intentionally attached to the object is also part of the mark; for instance, a flag, a long antenna or a swimming platform. This also includes something tem- porarily attached such as a Whaler tied up to the race committee boat, or a “keep-off buoy” hung off the transom of the race committee boat to keep boats farther away. However, the race committee’s anchor line is not part of the mark.
MA R K - R O OM 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.
This definition is central to applying rule 18 (Mark-Room). It describes the “space” (see definition Room) a boat needs to give another boat when one of
