The **Q flag**, or quarantine flag, is the signal flag of the letter Q in the International Code of Signals: a plain yellow rectangle. Flown alone by a vessel entering port, it signals ‘My vessel is healthy and I request free pratique’, that is, permission for the crew and passengers to come ashore. Historically the same flag was used to declare quarantine; modern usage is the opposite.
**Example**: A yacht making her landfall raises a yellow Q flag at the starboard spreader to request clearance from customs and health authorities.
**See also**: [signal-flag](/glossary/signal-flag/), [courtesy-flag](/glossary/courtesy-flag/), [ensign-at-sea](/glossary/ensign-at-sea/), [hoisting](/glossary/hoisting/)