Aiming is a combination of sight alignment and sight placement.
Sight alignment is the centering of the front sight in the rear sight. The top of the front sight must be level with the top of the rear sight. To align your sights, first center the front sight and then raise or lower it to make the front and rear sights level.
Sight placement is correctly placing the front sight on the target where you wish to hit the target, without disturbing your sight alignment. For target shooting, the "six o'clock" hold is generally used. This is done by placing the dot on top of the aligned sights. For defensive shooting, your point-of-aim will generally be your point-of-impact. In other words, after properly aligning your sights, cover the point you wish to hit with the front sight.
The eye can only focus on one distance at a time. Your point of focus should be the front sight. Not the rear sight, and not the target. This will result in the rear sight and target appearing hazy, but it is the only way to maintain proper sight alignment.
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