During holidays, at regattas or on other special occasions, dressing a ship in brightly colored flags has been a long and fun tradition. Not only does it look festive, but it also pays homage to centuries of maritime history. The flags which are used for dressing ships are known as the International Code of Signal Flags, often called alphabet flags because each flag represents a particular letter or number.
Different countries have different traditions for the order of flags, and the order is also different depending on whether it is a naval vessel or private vessel. However, in the U.S., Chapman’s Piloting & Seamanship recommends the following order for dressing a private vessel with signal flags starting from the front of the boat:
AB2, UJ1, KE3, GH6, IV5, FL4, DM7, PO3rd Repeater, RN1st Repeater, ST0, CX9 WQ8, ZY2nd Repeater
The idea is to create a pleasing pattern of colors with two flags (letters) followed by a pennant (number), repeated over and over from bow to stern. The string of flags should be raised to the masthead.
In addition to the string of signal flags, the national ensign should be flown at the stern staff, from 8 am to sunset. For sport fishing boats, it can be impractical to fly the national ensign from a stern flagstaff, so the ensign may be flown from the aft part of the superstructure.
Maritime signal flags have a rich history, dating back to at least 1500s, when the use of banners were flown as a form of communication at sea. By the mid-17th century, the Duke of York developed a unified system of naval codes which eventually became the International Code of Signals we know today.
Each letter is represented by a particular flag which has a specific meaning. In addition, there are separate numeric pennants which when used with letter flags, convey different messages. For example, if a ship is using the Medical Signal Code of “BR 2” (two flags and a pennant) the vessel is stating that it requires a helicopter urgently with a doctor. When used in combinations like the previous example, the alphanumeric flags can literally convey thousands of messages!
As a boater there is no real neccessity to know the meaning of all the flags. However, a few are important to know. The letter “A” or Alfa is the international signal for “diver down, keep well clear at slow speed,” the letter “Q” or Quebec means “Pratique” and must be flown when first entering a port of another country (t is a request to be boarded by the customs agent of that country and be given clearance) and the letter “O” or Oscar means “man overboard” (seen attached to the MOB pole).