Breastworks were above-ground trenches. Earth, rocks, sandbags, masonry, tree trunks and any other material that could be found in the area was used to provide cover for 7 to 8 feet high trenches. It some places breastsworks were as high as 30 feet. Breastworks were usually built on top of water-logged ground where it was difficult to dig trenches. In breastworks dugouts were made by leaving a space for a shelter and then having it roofed.
The trench was not a trench at all. The bottom may have been two feet below ground level. An enormous breastwork rose in the darkness some ten or more feet high. All about us there was an air of bustle. Men were lifting filled sandbags on to the parapet and beating them into the wall with shovels. Bullets cracked in the darkness. Every now and then a figure would appear on the skyline and drop skillfully on the firestep.
The fortification consists of breastworks, built up high to the front, with just a little shallow trench dug behind. The reason is that drainage is so difficult. These breastworks are made of millions of tightly-made sandbags laid one upon the other, packed well together. Every eight yards there is an island traverse, a great mound of earth and sandbags strengthened by rivetting, round which the trench winds. This is to localise the explosion of shells or prevent an enemy who might reach the flank being able to pour fire right down the length of a trench. There are communication trenches back every few yards and innumerable succeeding lines for the main army. The whole network extends in most places for three or four miles. The dug-outs are all in lines, but mostly along the communication trenches.
When there is no excitement there are about two sentries to every sector of say 9 yards on watch, and one officer for the company. The rest are in the dugouts. When a bombardment comes or there is a gas alarm, everyone rushes out and takes what cover one can in the front trench, awaiting developments. Against the front breastwork we have a step, about two feet high, upon which men stand to shoot. When there is a bombardment nearly everyone gets under this step, close in against the side.