The observation is conducted through a small loophole made by a stick through the parapet or an iron tube run through and directed toward the point to be observed. To conceal the exit a few tufts of earth and grass are placed there in an irregular manner. Steel loopholes may also be employed for observation and firing purposes. They may be arranged a yard or two apart, so that one man observing through one can direct his mate using the rifle at the other so that he may bring fire to bear upon any member of the enemy's force that exposes himself at the point under observation. The loopholes, both observation and firing, are arranged slantwise in the parapet so that the observer does not look straight to his front nor does the firer fire in that direction. An aiming rack constructed so as to resist the recoil of the rifle and not derange its aim on firing may be arranged near the observation loophole. When the enemy exposes himself all that is necessary is a press on the trigger and the bullet goes straight to its mark. Such an aiming rack may be easily constructed, as shown in Plate 44. Observation of the enemy trenches may also be effected by use of the periscope or, in the absence of one of these, by a looking glass in a slanted position fastened to a stick planted at the rear wall of the trench and protruding over the parapet, to reflect his trenches. (See Plate 45.) FIELD GLASSES The enemy's trench usually appears completely deserted, but on observing it through field glasses you are astonished by the details revealed. You will see, from time to time, the eye of the enemy observer who shows himself at the loophole, or any other activity that it is capable of being observed from the outside. The observer watching through the field glasses will soon become so familiar with the appearance of the opposing trenches that he will be able to detect immediately any alteration in the obstacles, or changes that may be made, such as the establishment of new listening or observation posts, new sap heads, machine-gun emplacements, etc. Observers are charged especially with detecting the location of machine-gun emplacements. The examination should be so complete and detailed as to prevent their existence without their location being accurately known. Any observations of enemy activities, of any nature whatever, are reported immediately so that they may be passed on to the commander whose unit is manning the trenches directly opposite the same. Loopholes should be screened at the rear by a sandbag split and hung over them. They should be carefully concealed to prevent their location being discovered by the enemy. There must be no alteration in the parapet where they are located. [Illustration: Plate 45.--Looking-glass periscope.] [Illustration: Plate 45a.--Trench showing wire overhead cover and wire trapdoor obsctacle. Machacoulis gallery in background.] SNIPERS