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