1. the insignia denoting her class;
2. at all international events, except when the boats are provided to all competitors, national letters denoting her national authority from the table below. For the purposes of this rule, international events are World Sailing events, world and continental championships, and events described as international events in their notices of race; and
3. a sail number of no more than four digits allotted by her national authority or, when so required by the class rules, by the class association. The four-digit limitation does not apply to classes whose World Sailing membership or recognition took effect before 1 April 1997. Alternatively, if permitted in the class rules, an owner may be allotted a personal sail number by the relevant issuing authority, which may be used on all the owner's boats in that class.

National authority            Letters
Algeria                       ALG
American Samoa                ASA
Andorra                       AND
Angola                        ANG
Antigua                       ANT
Argentina                     ARG
Armenia                       ARM
Aruba                         ARU
Australia                     AUS
Austria                       AUT
Azerbaijan                    AZE
Bahamas                       BAH
Bahrain                       BRN
Barbados                      BAR
Belarus                       BLR
Belgium                       BEL
Belize                        BIZ
Bermuda                       BER
Bolivia                       BOL
Botswana                      BOT
Brazil                        BRA
British Virgin Islands        IVB
Brunei                        BRU
Bulgaria                      BUL
Cambodia                      CAM
Canada                        CAN
Cayman Islands                CAY
Chile                         CHI
China, PR                     CHN
Chinese Taipei                TPE
Colombia                      COL
Cook Islands                  COK
Croatia                       CRO
Cuba                          CUB
Cyprus                        CYP
Czechia                       CZE
Denmark                       DEN
Djibouti                      DJI
Dominican Republic            DOM
Ecuador                       ECU
Egypt                         EGY
El Salvador                   ESA
Estonia                       EST
Fiji                          FIJ
Finland                       FIN
France                        FRA
Georgia                       GEO
Germany                       GER
Great Britain                 GBR
Greece                        GRE
Grenada                       GRN
Guam                          GUM
Guatemala                     GUA
Hong Kong, China              HKG
Hungary                       HUN
Iceland                       ISL
India                         IND
Indonesia                     INA
Iran                          IRI
Iraq                          IRQ
Ireland                       IRL
Israel                        ISR
Italy                         ITA
Jamaica                       JAM
Japan                         JPN
Jordan                        JOR
Kazakhstan                    KAZ
Kenya                         KEN
Korea, DPR                    PRK
Korea, Republic of            KOR
Kosovo                        KOS
Kuwait                        KUW
Kyrgyzstan                    KGZ
Latvia                        LAT
Lebanon                       LIB
Libya                         LBA
Liechtenstein                 LIE
Lithuania                     LTU
Luxembourg                    LUX
Macau, China                  MAC
Madagascar                    MAD
Malaysia                      MAS
Malta                         MLT
Mauritius                     MRI
Mexico                        MEX
Moldova                       MDA
Monaco                        MON
Montenegro                    MNE
Montserrat                    MNT
Morocco                       MAR
Mozambique                    MOZ
Myanmar                       MYA
Namibia                       NAM
Netherlands                   NED
Netherlands Antilles          AHO
New Zealand                   NZL
Nicaragua                     NCA
Nigeria                       NGR
North Macedonia               MKD
Norway                        NOR
Oman                          OMA
Pakistan                      PAK
Palestine                     PLE
Panama                        PAK
Papua New Guinea              PNG
Paraguay                      PAR
Peru                          PER
Philippines                   PHI
Poland                        POL
Portugal                      POR
Puerto Rico                   PUR
Qatar                         QAT
Romania                       ROU
Russia                        RUS
Samoa                         SAM
San Marino                    SMR
Saudi Arabia                  KSA
Senegal                       SEN
Serbia                        SRB
Seychelles                    SEY
Singapore                     SGP
Slovak Republic               SVK
Slovenia                      SLO
Solomon Islands               SOL
South Africa                  RSA
Spain                         ESP
Sri Lanka                     SRI
St Kitts & Nevis              SKN
St Lucia                      LCA
St Vincent & Grenadines       VIN
Sudan                         SUD
Sweden                        SWE
Switzerland                   SUI
Tahiti                        TAH
Tajikistan                    TJK
Tanzania                      TAN
Thailand                      THA
Timor Leste                   TLS
Tonga                         TGA
Trinidad & Tobago             TTO
Tunisia                       TUN
Turkey                        TUR
Turks & Caicos                TCA
Uganda                        TTO
Ukraine                       UKR
United Arab Emirates          UAE
United States of America      USA
Uruguay                       URU
US Virgin Islands             ISV
Vanuatu                       VAN
Venezuela                     VEN
Vietnam                       VIE
Zimbabwe                      ZIM

1. National letters and sail numbers shall be
   1. in capital letters and Arabic numerals,
   2. of the same colour,
   3. of a contrasting colour to the body of the sail, and
   4. of a sans-serif typeface. 
      In addition, the letters and numbers identifying the boat shall be clearly legible when the sail is set.
2. The height of characters and space between adjoining characters on the same and opposite sides of the sail shall be related to the boat’s overall length as follows:

Overall length      Minimum height     Minimum space between characters
                                       and from edge of sail
Under 3.5 m            230 mm                45 mm
3.5 m -- 8.5 m         300 mm                60 mm
8.5 m -- 11 m          375 mm                75 mm
Over 11 m              450 mm                90 mm

1. General
   1. Class insignia, national letters and sail numbers, where applicable, shall be placed on both sides and such that those on the starboard side are uppermost.
   2. National letters shall be placed above the sail numbers on each side of the sail.
2. Mainsails
   1. The class insignia, national letters and sail numbers shall, if possible, be wholly above an arc whose centre is the head point and whose radius is 60% of the leech length.
   2. The class insignia shall be placed above the national letters. If the class insignia is of a design that it may be placed back to back, then it may be so placed.
3. Headsails and Spinnakers
   1. National letters and sail numbers are only required on a headsail whose foot length is greater than 1.3 x foretriangle base.
   2. The national letters and sail numbers of headsails shall be displayed wholly below an arc whose centre is the head point and whose radius is 50% of the luff length and, if possible, wholly above an arc whose radius is 75% of the luff length.
   3. The national letters and sail numbers shall be displayed on the front side of a spinnaker but may be placed on both sides. They shall be displayed wholly below an arc whose centre is the head point and whose radius is 40% of the foot median and, if possible, wholly above an arc whose radius is 60% of the foot median.