It is usually composed of four or five fronts, but it may be applied to a polygon of any number of sides.
For the details of the construction of these several works, we must refer to the special treatises on field-fortification.
Lines of intrenchments may be made either continuous or with intervals.
In adopting either plan, the engineer should avail himself of all the natural obstacles presented by the position, so as to diminish the labor of erecting artificial means of defence.
The simplest arrangement for a continuous intrenchment is the _cremailliere_ or indented line.

When applied to an irregular site, or used to connect together distant and detached works, the indented line may be regarded as a good disposition.

Mitres and redans, connected by straight curtains, are sometimes employed, as also a combination of large and small redans, forming alternate salient and re-entering angles.

A continuous line of bastions is preferable to any other arrangement, when there is plenty of time for their construction.
Lines with intervals are frequently formed of alternate lunettes and square redoubts.

Other detached works may be employed in the same way.
This manner of intrenching a position has several advantages, with disciplined troops.