Number Pennants

The International Code of Signals provides ten numeral pennants (0 to 9) alongside the 26 alphabetical flags, three substitutes, and the answering pennant. Numerals spell out bearings, courses, dates, latitude and longitude, depths, and times in single-flag and multi-flag hoists, and the substitutes repeat a flag already shown in a hoist without carrying a duplicate aboard. The system lets two vessels with no common language exchange defined signals by flag alone.