A Command is the vertical elevation of one work above another, or above the country.
A Command in front is when an eminence is directly facing the work which it commands.
A Command in the rear, or reverse, is when any eminence is directly behind the work which it commands.
A Command by enfilade is when an eminence is situated in the prolongation of any line of a work, and a considerable part of it may be seen from thence; this line will be subject to enfilade, and such a command is the most dangerous.
The Rampart (A T R) is an elevation of earth, obtained from the excavation of the ditch; and is that part of the fortification which is situated between the ditch, and the town, consisting of an interior slope, terreplein, banquette, parapet, and exterior slope or escarp.—(Vide [Plate.])
The Interior slope (A) is the inclination of earth nearest to the town.
The Terreplein (T) is the upper part of the rampart, which remains after having constructed the parapet.
The Parapet (R) is a mass of earth elevated on the terreplein of the rampart, on the side towards the country; being from 18 to 22 feet thick, and from 6 to 8 feet high. The top is formed with a slight declivity towards the country, which is called the superior slope.
The Banquette is an elevation of earth, or step, on which the soldiers stand to fire over the parapet.
The Revetment is the masonry which retains the earth of the rampart on its exterior side. It is about 5 feet thick at the top, and its slope is one-fifth, or one-sixth its height.