An object the sailing instructions require a boat to leave on a specified side, and a race committee boat surrounded by navigable water from which the starting or finishing line extends. An anchor line or an object attached temporarily or accidentally to a mark is not part of it.

Mark-room Edit

Room for a boat to sail to the mark, and then room to sail her proper course while at the mark. However, mark-room does not include room to tack unless the boat is overlapped to windward and on the inside of the boat required to give mark-room.

See also rule 18.

The video below brings clarity to what is meant by that tiny little word "at" in the above definition. When a boat must start to change course in order to round the mark on her proper course then she is "at" the mark. Unfortunately this is not a printed definition and so we might expect to see a call book addition at some point in time to make this abundantly clear.

The important point with this definition of mark room is that "room to sail her proper course while at the mark" does include room to make a so-called tactical mark rounding.

thumb|300px|right|Giving room "at" the mark
File:Mark room tack upwind.gif
File:Mark room gybe upwind.gif
animated illustrations wanted