A watch house (also known as watch house, guard building, guard body, building security, sentinel building or security gate) is a construction used to house security personnel and equipment. Guardhouses have historically been dormitories for sentries or guards, and places where sentries not posted at sentry posts wait "on guard", but more recently they are staffed by a contracted security company. Some guard houses also function as prisons.[1][2]​.

In the Ludwigsburg Fortress in the 19th century, guardhouses were places where sentinels were posted to eat and sleep between guard periods at the 21 sentinel posts around the city. The city had five guardhouses (the Dauphine Gate, the town's entrance to the King's Bastion, the Queen's Gate, the Maurepas Gate and the Pièce de la Grave), and even if they did not sleep, the sentinels would be "on guard" of those guardhouses in case of need.[3]​.

At the Fort Scott National Historic Site guardhouse, typical furniture for the guardrooms included benches, tables, shelves, a platform bed for men resting between assignments, arm racks, a fireplace or stove, and leather buckets (used for fighting fires, another task). of guards). The prison cells were unfurnished and contained simply a garbage can and iron rings on the walls to hold the shackles.[4]​.

In 20th century commercial, industrial, institutional, government or residential facilities, guard houses are usually placed at the entrance as control points to secure, monitor and maintain access control to the secure facility.[5]​ In the case of small to medium sized facilities, generally, the entire physical security envelope is controlled from the guard house.

One of the general orders of a sentry in the United States Navy and Marine Corps is to "Repeat all calls more distant from the guardhouse than mine." The guardhouses thus serve as central communications centers for the peripheral sentry posts, where the corporal of the guard is stationed. When sentries are relieved by their replacements, the sentry stationed at the Guard House, designated "No. 1", is conventionally relieved first.[6][7]​.