=2. Allocation of Frontages and Objectives.=--Both in attack and defence a definite frontage in the field of fire--termed a _sector_--should be allotted to each fire-unit by company and platoon commanders. Thus the enemy appearing in any given sector will at once be engaged by the unit to which that particular sector has been allotted. Each fire-unit commander on receiving orders as to his frontage, will indicate it to his unit in the manner described in the following paragraphs, and must make sure that the N.C.O.’s, observers, and men of his unit clearly understand the extent and limits of their sector. =3. Indicating the Limits of Sectors= (Fig. 47).--The limits of each sector will be indicated by means of suitable description points (see Sec. 45, para. 3) on each flank of the frontage allotted to an unit. These description points should, as a rule, consist of distant features of a landscape or of the field of fire. If no suitable description points mark the limits of a sector exactly, the limits will be indicated as being so many hand or finger breadths (Sec. 45, para. 7) to the left or right of the nearest suitable description point. The limits of sectors may be made to overlap in the same manner. In defence there will generally be ample time for allotting frontages. In attack frontages will usually be allotted on deployment, but whenever possible they will be selected beforehand by preliminary reconnaissance. =4. Object of Overlapping the Sectors.=--The overlapping of sectors insures that the entire front is kept under close observation, and that no part of it remains unswept by fire should occasion arise for delivering fire at a target in any part. It also prevents waste of ammunition and loss of fire effect through units firing at objectives outside their own sectors unless this is necessary for the purpose of mutual support. =5. Example of Field of Fire divided into Sectors.=--(i) Fig. 47 shows a field of fire divided into overlapping sectors by the use of description points. The sketch illustrates the arrangements made, as the result of a hasty preliminary reconnaissance, by a company commander for fire action by the four sections or normal fire-units of his command on deployment in the early stage of attack. In defensive positions similar arrangements may be made for indicating sectors allotted to each locality. Defensive positions will usually include a number of localities of special tactical importance. From these localities either direct or flanking fire, or both, is brought to bear on all ground over which the enemy may advance. As long as this is done the intervening ground between localities need not be held in a continuous line.