What is a work usually in the form of a redan, to inclose a space before a door or staircase, or at the gorge of a larger work. It is arranged like a stockade called?

tambour — (Fort.) A work usually in the form of a redan, to inclose a space before a door or staircase, or at the gorge of a larger work. It is arranged like a stockade. (Webster's 1913.)

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