J. P. Cole, Military Instructors Manual
“ Patrols.—A. It is the duty of all the troops holding the front lines to establish a command of the ground in front of their parapet up to the enemy's wire. This can be done by extended and constant patrolling by night and reconnaissance by day so that the ground is thoroughly well known to as large a portion as possible of officers and men and so no enemy can move or remain in his front by night or day without detection. One of the particular duties of these patrols is to observe the condition of the wire entanglements. ”
