A Gabion is kind of a whicker basket filled with earth, and used to hide behind.  They absorb bullets wonderfully.

The morning gun or a response to an enemy advance?  A Sergeant rises atop the barricades at first light to investigate. A grim looking veteran from one of the Mid-Atlantic states walks across the gabions. Gabions are simple woven tubes of wythes and limbs put together to create a modular defensive position. The structure can be fabricated well behind the lines of battle and brought forth & planted into the ground and filled with earth and rocks, forming a veritable instant wall. The sizes varied, but below is a quote from Gen. Washington's General Orders at Yorktown:

Head Quarters before York, Saturday, October 6, 1781
...33. The Infantry are to make the number of Gabions &ca. ordered them.
34 The Gabions are to be three feet high including the end of the Pecquetts which are to enter the ground, they are to have two feet and a half diameter and be formed of Nine Picquetts, each of two and a half inches circumference interlaced with branchery, striped of leaves to be equally closed at top and bottom, in order that they may not be larger at one end than the other...