Infantry manning a trench can assist listening by digging a small pit, 6 feet deep below the trench, and running a bore-hole out 20 feet or more.
The enemy is always listening for indications of the direction and position of gallery heads. Work must therefore be carried on with a minimum of noise. Shouting down the shafts of galleries is absolutely forbidden.
When the mining operations of the enemy are detected a report should be made at once to the officer in charge of that section of the trench.
Chapter IV
FIELD TRENCHES
The next element of the defensive position is the first line fire trenches. These are located so as to have a good field of fire to the front for several hundred yards and so constructed as to give the greatest cover and protection from the fire of the enemy.
An unbroken, continuous trench would be exposed to enfilade fire. A shell, shrapnel or grenade bursting therein would have widespread effect. To overcome these elements the trench is constructed in short lengths, with traverses between them, and technically known as the traverse type.
Better defilade is thus secured and the material effect of any burst is confined to narrow limits.