sentry box
From Longman Dictionary of Contemporary EnglishRelated topics: Militarysentry boxˈsentry box noun [countable] PMa tall narrow shelter with an open front where a soldier stands while guarding a buildingExamples from the Corpussentry box• Yet once behind the sentry box, guilt and failure lay stacked on the barrack square.• The club entrance was dark; there was no guard in the sentry box, and the gate was open.