International signal letter "Q" flag. On arrival at a foreign port, the owner or captain of a yacht (any size) should report to the authorities. The "Q" flag (plain yellow) should be flown where it can be easily seen: starboard spreader, radio antenna, fishing outrigger, etc.- to indicate that the vessel desires to be boarded by customs and other governmental authorities. When reporting, the crew and guests should remain aboard until permission (pratique) has been granted to land. Once pratique has been granted, the "Q" flag may be lowered, and the courtesy flag of that nation may be hoisted. Quarantine flags are not used for trips between the United States and Canada on the Great Lakes.