Adjust backsight to correct range of target and lay gun on mark. If gun is nearer than 900 yards, raise sight by 400 yards, and if further than 900 yards, raise sight 250 yards. The new line of sight gives safety angles. When heads of own troops come into line of sight, cease fire, or continue to elevate gradually, keeping pace with advance. Indirect Fire. Firing from concealed positions at an auxiliary aiming mark. A machine gun protractor, or graticules cut across the focal plane of prismatic glasses are most satisfactory. By this means indirect fire can be applied as easily as direct fire. Night Firing. The gun may be laid by day and left until required, or by use of the “night firing box,” as follows:— A stick is placed in the ground 10 yards in front of gun in a direct line with the target, and at night the stick is replaced by the “night firing box”—the sights altered (but not the gun) until aligned on the lamp at the point where the lines form the true centre. Searching and deflection can be satisfactorily carried out with this apparatus. EXAMPLES OF FIRE ORDERS. Normal Fire Order using One Elevation. Range. Aiming mark. Fire (signalled). Cease fire (signalled). Changes in elevation (up or down 100), as required. Combined Sights. Range and differences. Aiming mark. Fire (signalled). Changes in elevation (left gun up 200, right gun down 200) (or more, as required). When Brigaded within Hearing. The B.M.G.O. issues fire orders direct to the Nos. 1 as above. When “differences” “by sections” are required the fire order will be as follows:— B.M.G.O. (_a_) By sections—Range—Differences. (Pause for section officers to name the number of their sections and the “range” for their sections; they do not repeat the “differences.”) (_b_) Aiming mark. (_c_) Fire. Traversing Fire. Range. Target (naming right and left limits to be traversed). “Inwards traversing.” Fire (signalled). The same method is employed when laying on the centre, the caution “Outwards traversing” being given. When brigaded within hearing orders are issued as follows:— By B.M.G.O.:— Range. Limits of traverse. Fire (signalled). Section officer repeats limits to be traversed, and immediately issues orders respecting ground to be traversed by their own sections, corresponding to their own positions. Vertical Searching Fire. Range. Aiming mark. To “range” vertical searching. Fire (signalled). Bracketing Fire. Ranges—bracketing. Aiming mark. Fire. SIGNALS. In many cases observation will be impossible from the gun position and it will be necessary for observers to signal results from a flank. The following semaphore code is used in signalling the results of observation of fire:— P— Plus: meaning fire observed at least 50 yards beyond target.