All the works comprehended between the capitals of two adjacent bastions is termed a _front_: it is taken as the unit in permanent fortification.
Fig.

39 represents the ground plan of a modern bastioned front, of a regular and simple form, on a horizontal site.
_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_.