31 Touching a Mark
31.1 While racing, a boat shall not touch a starting mark before starting, a mark that begins, bounds or ends the leg of the course on which she is sailing, or a finishing mark after finishing.

31.2 A boat that has broken rule 31.1 may, after getting well clear of other boats as soon as possible, take a penalty by promptly making one turn including one tack and one gybe. When a boat takes the penalty after touching a finishing mark, she shall sail completely to the course side of the line before finishing. However, if a boat has gained a significant advantage in the race or series by touching the mark her penalty shall be to retire.