Normally two aiming posts are placed out to establish the aiming line. The rounds are fired from the mortar in reference to this line. After the mortar has been mounted and laid on the direction stake, the sight is normally refereed to 2,800 mils, and the aiming posts are placed along this line of sight. The aiming posts are placed on the new line of sight by the first ammunition bearer, observing the arm-and-hand signals (fig. 14-14) of the gunner. The posts are called the far post and the near post. The far post is placed out 30 to 50 meters from the mortar, and the near post is placed at 15 to 30 meters (fig. 14-15). When this is not possible, because of terrain or situation, the post should be placed out as far as possible, keeping in mind that the distance between the two posts must be equal. The far post is always placed first and the near post last. When these two posts are seen through the sight, they appear as one. This is called

Figure 14-15.-Aiming post and lights (M58/M59).

Figure 14-16.-Aligned sight picture.

the ALIGNED sight picture (fig. 14-16). If the two aiming posts do not appear as one, displacement of the sight or the baseplate has occurred. This separation is caused by one or two things: either (1) a large deflection shift that moves the entire sight out of the plane passing through the aiming posts; or (2) a lateral (left or right) displacement of the baseplate caused by the shock of firing, which also moves the sight out of the plane of the aiming post. When both the far post and the near post are visible, it is called a COMPENSATED sight picture (fig. 14-17).