The International 420 Association has very specific rules and regulations with regards to the design of all 420s and their equipment and this allows the class to remain as a One Design class even where boats are manufactured by different companies around the world. The link below will take you to a webpage on the International 420 website where all class rules can be accessed. This is most often used if sailors are adding numbers or national flags to their sails.
Major international events, and sometimes the National Championships in some countries, will require boats to be measured to check compliance with the class rules. When the class association sends teams to events the coach will give guidance to the sailors as they go through the measurement process. It is important that sailors bring the measurement certificates to these events where this is requested on the Notice of Race.
The Racing Rules of Sailing (RRS) governs the overall sport of sailboat. It is revised and published every four years by World Sailing and the link below will take you to the World Sailing website.