d 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.

A _horn-work_ consists of a front of fortification, and two wings
resting on the faces of bastions of a front of the fortress. It
sometimes has also a demi-lune or bonnet, as in the case of
demi-tenaillons. (Fig. 43.)

A _crown-work_ consists of two fronts of fortification, and two wings.
(Fig. 44.) It is sometimes made _double_, and even _triple_.

These works are also employed as advanced works, and placed entirely in
front of the glacis. They have generally been added to a fortress for
the purpose of occupying some important piece of ground not included
within the limits of the main work. They may be constructed with covered
ways, and sometimes it may be found advantageous to secure them by
retrenchments.

A _detached work_ may be made in any form deemed best suited to the
site. Being but remotely connected with the fortress, the latter will
exercise but slight influence on the character of its plan or
construction. They are usually of limited ext