A ship's brig is a jail or prison used to house individuals that pose a security threat to the vessel or her crew. These individuals may comprise prisoners of war, criminals, or crewmembers serving or are awaiting to serve punishment. The size of the brig is dependent of the size of the ship. Smaller craft like the Defiant class have only one cell, while bigger vessels like the Normandy class have ten or more. Cells are designed to hold two prisoners at a time, although four can be housed in one in emergency situations. Starfleet cell design calls for bulkheads on three sides and a fourth housing an embedded forcefield to allow passage in and out of the enclosement. Cells also have hide-a-way bunks and tables, but are not made for long-term incarceration.
Usually the brig is located in an isolated area of the ship or station, and includes a security checkpoint from which access to the prisoners are controlled. This point is manned at all times by Security Officers and has extensive sensor monitoring, as well as a weapons locker. Most ship and station designs have brigs as part of a larger security complex.
The brig is under the command of the Brig Officer, who is responsible for the security and welfare of prisoners housed therein.