Fig. 4a
The rear sight, C, the front sight, B, and the bull's eye, A, are all on a line with the eye, D, the rear sight being set for 200 yards.
Suppose we wanted to shoot at 2000 instead of 200 yards. We would raise the slide up to 20 (2000 yards) on the sight leaf.
In order to see the bull's eye through the notch sight at 2000, we must raise the eye to the position, D. We now have the rear sight, the bull's eye and the eye in line, but we must bring the front sight in line with them, which is done by raising the muzzle of the piece, giving the result shown in [Fig. 4a].
[1351]. Line of sight. With the open sight the line of sight is determined by a point on the middle line of the notch of the rear sight and the top of the front sight.
With the peep sight, the line of sight is determined by the center of the peep and the top of the front sight.
Kinds of sights
[1352]. (See [Fig. 3], [par. 1343], giving rear sight leaf in detail.)
The different kinds of sights are as follows:
(a) Open sight. By open sight is meant the use of any one of the sighting notches.