HORN-Work (ouvrage à corne), in fortification, an outwork composed of a front and two branches; the front consisting of two half bastions and a curtain. This work is of the nature of a crown-work, but smaller, and serves the same purposes. The use of horn-works, in general, is to occupy some rising grounds in advance of the principal fortification, the distance of which determines that of the horn-work; and they are placed either before the curtain or before the bastions, according to circumstances.