Meritorious mast awards are used as official recognition for a job well done. They are used in the United States Navy to recognize enlisted members who have performed above and beyond their usual requirements of duty or have displayed exceptional judgement or initiative.
In this context, a "mast" is an assembly of the crew of a ship for a variety of purposes. The term dates back to the days of sailing ships when naval justice was dispensed on the weather deck beside the ship's mainmast. Though ships no longer have mainmasts or weather decks, the term "mast" remains to refer to a gathering of the ship's crew.