A brig was a two masted square-rigged sailing vessel which also carried a large gaff sail (brig-sail or spanker) on the aft mast (mainmast). It also carried staysails (gibs) from the foremast to the bowsprit and late in its career was capable of setting studdingsails on extensions to the yards which, allied with the a narrow hull and sharp (or clipper) bow, gave the brig a fair turn of speed in the right conditions.
The brig grew out of the Mediterranean brigantine in the 16th to 17th centuries as a relatively short-haul cargo vessel suited to [[Atlantic] conditions. Being relatively small, it was relatively cheap to operate because of small harbour dues and ease of handling. It was also used by navies as a despatch and training vessel and carried up to about 20 guns.
In the 19th century longer voyages were made with brigs, frequently carrying freight and immigrants across the Atlantic to America. However, in the 1860s, this role began to be taken over by the larger barque, although brigs were still being built well after the advent of steam.
The “hermaphrodite brig”, sometime known as a “brig-schooner” is a cross between a brig and the historic brigantine. It carries only fore-and-aft sails on the mainmast, whereas the brig is square-rigged and the “true” brigantine carries square-rigged top-sails above the spanker. Just to complicate things further, these days the hermaphrodite brig is also known as a brigantine.
A brig is also a holding cell onboard a ship.
- Square-rigged refers to the set of the sails on what most people would consider the classic large sailing ship – the galleon or the clipper for example, or any large warship of the age of sail. The sails are set across the bow to stern line of the vessel and are four-sided and attached to yards that can be angled according wind direction. (Very few vessels in the last 500 years have been purely square-rigged – almost every ship has had triangular staysails set between the masts or from the foremast to the bow and most have a gaff-sail on its stern-most mast – usually called a “spanker” – whether or not there is square rigging on that mast.)
- Staysail: refers to a triangular sail set between two masts with two corners attached to the aftmost. (This corner is called the clew and it is here that the sail is trimmed by tightening or loosening it.) If set from the foremast it is called a headsail or forestaysail. If there is only one on the foremast that sail is called the jib. If more than one headsail, then jib refers only to the topmost.
- Studdingsails (pronounced "stuns'ls" were additional square sails set on booms on either side of the sails on a square-rigged vessel. They were only used in fine weather with the wind abaft the beam (that is, from behind a line drawn at right angles across the vessel) and their purpose was to get every last ounce of speed out of the vessel, by increasing the sail capacity.
- Fore-and-aft rigging refers to sails that are set along a line between bow and stern of a vessel. Obviously, depending on the direction of the wind in relation to the intended course of the ship, those sails attached to booms and/or gaffs will be set at some sort of angle. Your standard yacht has fore-and-aft rigging.