A combination of the two methods may be necessary when, in using the second method, the reference point is not readily identified. Thus, in the case mentioned, it may, for example, be necessary to say: =Reference point at 1 o'clock, clump of trees on hill crest.= In both methods the sequence of commands laid down should be observed. Various devices for pointing out indistinct targets may be improvised and used. THE USE OF COVER. =142.= The recruit should be given careful instruction in the individual use of cover. It should be impressed upon him that, in taking advantage of natural cover, he must be able to fire easily and effectively upon the enemy; if advancing on an enemy, he must do so steadily and as rapidly as practicable, taking advantage of any available cover while setting the sights, firing, or advancing. To teach him to fire easily and effectively, at the same time concealing himself from the view of the enemy, he is practiced in simulated firing in the prone, sitting, kneeling, and crouching positions, from behind hillocks, trees, heaps of earth or rocks, from depressions, gullies, ditches, doorways, or windows. He is taught to fire around the right side of his concealment whenever practicable, or, when this is not practicable, to rise enough to fire over the top of his concealment. When these details are understood, he is required to select cover with reference to an assumed enemy and to place himself behind it in proper position for firing. =143.= The disadvantage of remaining too long in one place, however good the concealment, should be explained. He should be taught to advance from cover to cover, selecting cover in advance before leaving his concealment. It should be impressed upon him that a man running rapidly toward an enemy furnishes a poor target. He should be trained in springing from a prone position behind concealment, running at top speed to cover and throwing himself behind it. He should also be practiced in advancing from cover to cover by crawling, or by lying on the left side, rifle grasped in the right hand, and pushing himself forward with the right leg. He should be taught that when fired on while acting independently, he should drop to the ground, seek cover, and then endeavor to locate his enemy; also that in the sun he is visible to a much greater degree than when in the shade. The instruction of the recruit in the use of cover is continued in combat exercises of the squad and platoon, but he must then be taught that the proper advance of the platoon or troop and the effectiveness of its fire is of greater importance than the question of cover for individuals _should the two considerations conflict_. He should also be taught that he may not move about or shift his position in the firing line except to get a better view of the target. OBSERVATION.