Sally port

A sally port is a secure, controlled entry way to an enclosure, e.g., a fortification or prison. 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. It may include two sets of doors that can be barred independently to further delay enemy penetration.

From around 1600 to 1900, a sally port was a sort of dock where boats picked up or dropped off ship crews from vessels anchored offshore. That meaning occasionally still occurs, especially in coastal Great Britain.