(a) Observers: 1. Must be men of infinite patience, keen hearing and eyesight. 2. They are located behind the first line in positions combining good view with concealment. 3. Each is provided with a panoramic map, made from aeroplane photographs, of the enemy's trenches. On this must be promptly noted every slightest change in the trace, height of parapet, etc., of the enemy's line. Such notes greatly assist in locating machine gun emplacements. 4. Each observer will also record in a note book everything of importance, with the time observed. 5. A report of changes, with an abstract of observer's notes, is forwarded daily to regimental headquarters. (b) Watchers (sentinels): 1. Stationed, one near the door of each dugout, in the first line, support and intermediate trenches. 2. They must be carefully concealed. 3. They must watch over the parapet (never through slits or loopholes) so as to have unrestricted view. 4. They are furnished with signal rockets and flares for prompt communication with the artillery, and have authority to use them. 5. Double sentinels are posted at night. (c) Listening Posts: 1. Located, usually in shell holes, just inside the entanglements. Connected with front line by tunnels. Protected from grenades by heavy gratings, when possible, and by concealment. 2. Occupied by 4 men (1 in command), in 3 reliefs. Usually occupied only at night unless our trenches are on a reverse slope. 3. Chief function is protection of the entanglements. (d) Microphone Posts.--Installed usually behind the first line. Intercept the enemy's telephone and ground-telegraph messages and any loud conversation in his trenches. (e) Fixed Patrols.--Generally remain in shell holes in front of our entanglements. (f) Reconnoitering Patrols: 1. Composed of from 3 to 5 men, commanded by a non-commissioned officer. Sent out at night only. 2. The company commander must promptly notify commanders of adjoining companies of the dispatch of these patrols, their time of departure, route and probable time of return. 3. Men should be assigned to this duty by roster. F. TRENCH WORK: