If the night is dark, to avoid surprise, keep up firing: One man per section should fire in turn, from time to time varying the direction.
25.—Digging by enemy.
If digging by the enemy is reported, cease firing. Have it located, throw bombs followed by volleys. Notify sappers for counter mining.
26.—Watch for light of enemy's fire.
If enemy fires, note where light appears.
27.—Posting of sharpshooters.
Locate sharpshooters in advantageous posts behind the trenches (trees, etc.). Have them fire into the enemy's listening posts and into the enemy's trench, especially wherever light appears. These posts should not be occupied during the day.
28.—Patrols.
Send out patrols, stationary or mobile.