Signal flags provide a way to communicate information relating to safety, distress, medical, and operational information, especially when language difficulties arise. Each flag has a unique and complete meaning
Single-letter signals are used for urgent and important issues, or issues of very common use. Two-letter and three-letter signals are used for other messages.
Strung from the forward waterline over the bow to the masthead, then over the stern to the aft waterline, signal flags are used to dress ship for holidays or special occasions.
Old and new USCGC Mackinaws dressing ship