Sally port

The entrance is usually protected by some means, such as a fixed wall on the outside, parallel to the door, which must be circumvented to enter and prevents direct enemy fire from a distance.

A sally, ultimately derived from Latin salīre (to jump), or "salle" sortie, is a military maneuver, typically during a siege, made by a defending force to harass isolated or vulnerable attackers before retreating to their defenses.

[citation needed] An extract from a 19th-century dictionary of military terms describes a sallyport thus: those underground passages, which lead from the inner to the outward works ; such as from the higher flank to the lower, to the tenailles, or the communication from the middle of the curtain to the ravelin.

When sallyports serve to carry guns through them for the out-works, instead of making them with steps, they must have a gradual slope, and be eight feet wide.

A sallyport may be an enclosed garage type building or a securely fenced or walled open-air parking area.