sentry box

the sentry box; in military architecture; It consists of a small tower with loopholes or arrow slits; generally raised in the most salient corner of the bastion of a fortress; that serves as a shelter and protection for the sentinels that guard the enclosure. There were sentry boxes in the oldest European fortifications from the Middle Ages. It is believed that the first sentry boxes were made of wood; like the machicolations; and that were placed in times of war. At present, the same term is used to refer to international border crossing entries; like the San Ysidro sentry box between Tijuana; Mexico and San Diego; Gallery