Normally when images of an object are formed on the retina of the two eyes, the two fields of vision overlap to some extent at the centre and provide a perception of depth. But for aiming at a distant object, depth perception is not as important as the proper line of alignment. For arches and shooters, the main objective is to find the line of alignment of the target and not its depth because the distance of the target is usually known. Since our two eyes are separated by a distance, they give two separate lines of alignment which can never allow the archer to aim exactly at the target. But on closing one eye, the archer can aim at the target more precisely by aligning his eye with the tip of the arrow or gun sight and the target and shoot accurately.