In sea-coast defences, and sometimes in a land front for the defence of the ditch, embrasures are made in the scarp wall for the fire of artillery; the whole being protected from shells by a bomb-proof covering over head: this arrangement is termed a _casemate_. Sometimes double ramparts and parapets are formed, so that the interior one shall fire over the more advanced; the latter in this case is called _a faussebraie_. If the inner work be separated from the other it is called a _retrenchment_[44] and if in addition it has a commanding fire, it is termed, as was just remarked, a _cavalier_. [Footnote 44: The term _retrenchment_ implies an interior work, which is constructed within or in rear of another, for the purpose of strengthening it; the term _intrenchment_, on the contrary, implies an independent work, constructed in the open field, without reference to any other adjoining work.] The _capital_ of a bastion is a line bisecting its salient angle. 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.