They are usually placed a few yards in front of the ditch, and concealed by some slight covering.
_Abattis_ are tops and large limbs of trees arranged along the glacis of a work; the ends of the branches are lopped off and sharpened.
_Palisades_ are stakes some eight or ten feet long, with one end fastened in the ground and the other made sharp.

They are placed in juxtaposition and connected together by horizontal riband-pieces.

This arrangement is frequently placed at the foot of the counterscarp.

When the timbers are large and the work is intended as a part of a primary defence, it is called a _stockade_; when the stakes are placed at the foot of the scarp, either horizontally or inclined, they receive the name of _fraises_.
A _cheval-de-frise_ consists of a horizontal piece of timber armed with wooden or iron lances, which project some eight or ten feet.

It is much employed against cavalry, and on rocky soils serves as a substitute for palisades.
_Crows'-feet_ are small wooden or iron forms filled with sharp spikes.
They are thrown, with their points upward, on ground which is to be passed over by cavalry.
_Mines_ are sometimes used in connection with intrenchments, but more commonly in the attack and defence of permanent works.