FLANK, in Fortification, is a line drawn from the extremity of the face towards the inside of the work.
Or, flank is that part of a bastion which reaches from the curtain to the face, and defends the opposite face, the flank, and the curtain. See FORTIFICATION.
Oblique or Second FLANK, or FLANK of the Curtain, is that part of the curtain from whence the face of the opposite bastion can be seen, being contained between the lines rasant and fichant, or the greater and less lines of defence; or the part of the curtain between the flank and the point where the fichant line of defence terminates.
Covered, Low, or Retired FLANK, is the platform of the casement, which lies hid in the bastion; and is otherwise called the Orillon.