Sally port

The primary modern meaning for sally port is a small controlled space with two doors. Essentially, one must enter the space and close the first door before opening the second to proceed, rather like an airlock.

Etymology and historical usage

The word "port" is ultimately from Latin "portus" for door. Often the term postern is used synonymously. It can also mean an underground tunnel, or passage (i.e. a secret exit for those besieged).

A sally, ultimately derived from Latin "sallir" (to jump), or sortie, is a military maneuver, typically during a siege, made by a defending force to harass isolated or vulnerable attackers before retreating back behind their defenses. Sallies are common way for besieged forces to reduce the strength and preparedness of a besieging army; a sally port is therefore essentially a door in a castle or city wall that allows a troops to make sallies without compromising the defensive strength of the fortifications.

Targets for these raids included tools which could be captured and used by the defenders, labour-intensive works such as trenches and mines, and siege engines and siege towers. Sometimes enemy labourers were also targeted.

Modern usage

Modern personnel sally ports are used to control entry into highly protected and restricted military areas, i.e. nuclear weapons storage areas, highly sensitive (and large) conventional weapons storage areas, i.e. small arms, munitions, etc. Sally ports are also used to control entry to highly valuable civilian facilities such as currency or credit card manufacturing sites.

A guard in a protected location (today usually physically remote from the actual sally port) will have control over the middle space between the two doors; the operation of the doors of the sally port; and the movement of all persons, materials and/or vehicles through the sally port. This sally port guard will have the means to check the personnel escorts and/or the credentials of all those persons, materials and vehicles to be passed into the protected space through the first opened door, prior to its opening. He will then monitor the sally transit to ensure that: (1) no more that the maximum allowed number of verified individuals/materials or vehicles are permitted and actually do transit into the middle space at any one time; (2) that all persons vehicles and/or materials are cleared by the controller of the interior protected space (a second, separate individual from the controller of the sally port) to enter that secured space prior to the un-locking and/or opening of the second door; (3) that the first opened door to the sally port is closed locked and secured prior to unlocking and/or opening the second door; and (4) the guard will ensure that after the completion of a transit movement of persons, materials and/or vehicles through the sally port, that the middle space of the sally port is clear (empty) of all persons, materials, or vehicles prior to his securing (closing/locking) of the second door, to await the next movement through the sally port.

Sally ports must be used with caution and transit through them must be carefully monitored during any emergency or non routine movements. The greatest safety hazard in use of these passage ways is the danger of over crowding the middle space between the doors. Since the opening of either one of the doors, locks; and locks out, the ability to open the sally port’s other door (until the first opened door is both closed, and locked); there is the danger of overcrowding the middle space, when too many persons, vehicles or materials attempt to enter the middle space when the first door is opened.

Once the middle space is overcrowded it may be impossible to properly close and lock the first door, thereby also making it impossible to open the second door; which of course is the only way that people, vehicles or materials can successfully exit the controlled area. Even when the sally port has control design over-rides installed in the door controls and locking apparatus, the physical dimensions and layout of the door openings and the size of the middle space will act to hamper quick egress of a controlled space through a sally port type opening.

Because of this danger controlled spaces protected by sally ports usually have multiple sally port openings, safety zones within the controlled space (for internal evacuation w/o leaving the controlled area), and formally written and routinely practiced procedures for the evacuation of persons, vehicles or materials. There is also a continuously supervised and monitored, accounting of the total number of persons, vehicles or materials within the controlled space to ensure that the designed evacuation maximum (by whatever is the evacuation procedure) is never exceeded.

Sally ports are also used to restrict the flow of people to one at a time so that intruders cannot pass into the classified or secure area on a cleared person's coattails.

Military vehicular sally ports are similar to the personnel sally ports but have, of physical necessity, a large middle space to control the incoming/outgoing vehicle and personnel mounted in the vehicle. Mounted personnel are made to stand down and the vehicles are inspected by guards.

If the person or vehicle in the middle space is found to be unauthorized, the guard can "lock down" both gates trapping the individual in question until a guard or police response force can neutralize and remove the person and/or vehicle.

A sally port appears on the Coat of Arms of the Republic of Malta

In the modern court building a sally port secures the prisoners in a holding area or brings then directly from the jail area separating them from the court with entry through the sally port controlled by the bailiff.

In "supermax" correctional facilities, groups of inmate cells may be connected to central corridors via sally ports. An officer behind protective glass opens the port doors individually after verifying that the person is allowed to pass.

Source

* [http://members.tripod.com/nicolaa5/articles/Hector/hist/HEngin.htm Continuing Education Program - Royal City of Eoforwic]