"Nautical Flags" teaches you all signal flags which are used to communicate with messages, at times because radio silence is required. The system of international maritime signal flags is one system of flag signals representing individual letters of the alphabet in signals to or from ships. It is a component of the International Code of Signals.
Also known as signaling flags, they are a set of flags of different colors, shapes and markings which used singly or in combination have different meanings. The flags include 26 square flags which depict the letters of the alphabet, ten numeral pendants, one answering pendant, and three substituters or repeaters. Also used for sailing and races