A, A, A—­Is the enceinte, or body
of the place.
B—­The bastions.
C—­The main ditch.
D—­The covered ways.
E—­The re-entering places of arms.
F—­The salient places of arms.
G—­The demi-lune.
H—­The demi-lune ditch.
J—­The demi-lune redoubt.
L—­The ditch of the demi-lune
redoubt.
M—­The redoubt of the re-entering
places of arms.
N—­The ditches of the redoubts.
O—­The tenaille.
P—­The double caponier.
a—­The traverses.
b—­The sortie-passages.
c—­Stairs.
d—­Cut in the demi-lune to flank
the redoubt of the re-entering
place of arms.

Fig. 40 represents a section through the line mn’ of the preceding figure.

A—­Is the rampart. B—­The parapet. C—­The ditch. D—­The scarp wall. E—­The counterscarp wall. F—­The glacis. G—­The covered way. H—­The terre-plain. J—­The parade.

Sometimes half embrasures are cut in the earthen parapet of a fort, so as to sink the gun below the crest, and thus more effectually cover the men from the enemy’s fire.

But guns in embrasure have a far less extended field of fire than when mounted in barbette; moreover, the embrasures present openings through which an enemy may penetrate in an assault.  Owing to these objections, they are employed only for the protection of particular points; that is, where it is important to cover the artillerists from the enemy’s fire, or where the guns are to be used merely to protect a ditch, or to enfilade a road, &c.  The bottom of the embrasure is called the sole, the sides are called cheeks, and the mass of earth between two embrasures, the merlon.  Embrasures may be made either direct or oblique, according as the fire is required to be perpendicular or oblique to the parapet.

A coverport is a small outwork of any convenient form, erected immediately in front of a gateway, to screen it from the enemy’s fire.

A counterguard is a more extensive work, constructed in front of a part of the fortress itself, or of some other outwork of greater importance, which it is intended to cover.  These are sometimes called coverfaces, from their situation and object; but the former term is most commonly used.

Sometimes outworks, called tenaillons, consisting of one long and one short face, are placed on each side of the demi-lune of a front of fortification, for the purpose of prolonging the siege. (Fig. 41.)

Small, or demi-tenaillons, are frequently so arranged as to cover only one-half of the demi-lune, and then a bonnet constructed in front of the salient of the demi-lune. (Fig.42.) In this case the bonnet is flanked by the short faces of the demi-tenaillons; these short faces are themselves flanked by the demi-lune, while the bastions flank the long faces.