Because two eyes are looking at a point, this point can only be known after two lines, and one eye is a line, so it is more accurate to aim the line at the sight and the target. First, when people look at things with two eyes, they will have three-dimensional images, and they can clearly see the front, back, left and right positions of objects, while when they look at things with one eye, they are just plane images, only the left and right sides, and there is no front and back. The simplest example is holding a pen in one hand and a pen cap in the other. When they have two eyes, it is easy to hold a pen. But when using one eye, it looks aligned. In fact, the front and back positions of the pen cap and pen are not aligned. When shooting, as long as the bullet hits the left and right of the target, not the front and back, it is best to turn off one ... When shooting the second time, it is often three points on a line. The so-called three points are the target, looking forward and looking back. In fact, in actual operation, it is a line at 4 o'clock, looking forward and looking back. It's easy to aim with one eye, but it's difficult to focus on a line with two eyes, so close one eye ... try it yourself when shooting ... many things need to be understood by yourself.