Signal · composer

Flag hoist

Flags are read from the top down. Type letters or figures; a repeated flag is replaced by the substitute that points back to it.

Hoist

How substitutes count

The first substitute repeats the uppermost flag of the group of the same class (letters, or numeral pennants) directly above it; the second repeats the second; the third the third. In BOOK the second O repeats the second letter of the hoist, so it is shown by the second substitute. In AA the second A is the first substitute.

Rule: International Code of Signals, 1969 edition revised 2005 (US edition: NGA Pub. 102, 2020), chapter 1 (general instructions).