Fleche (French flèche, arrow), is the name given to a small redan, detached and isolated, whose faces are not more than 45 to 60 feet, f (fig. 18), the opening of the flanked angle varies from 60 to 80 degrees.
Arrows or fleches are constructed, at the foot of the glacis, upon the capitals of the bastions and half-moons. They are formed from two faces of 30 or 40 yards each within, which are flanked by the covered way (pl. 7 fig f and profile pl. 9 fig. 81). When they are constructed with gabions, they are soon made, and if fraised on the side of their ditch, and palisaded at the gorge, the besieger must storm before he can penetrate beyont them to lodge himself on the glacis.
Source: Lallemand, Henri Dominique: A Treatise on Artillery (New York 1820)