《孙膑兵法·十阵》
这就是雁形阵的作用。钩形阵的布列，前面必须排成方形，左右两翼相对应必须布成钩形。
三声既全，五采必具，辨吾号声，知五旗。
This is the function of the geese formation. The formation of the hook formation must be arranged in a square in front, and the left and right wings must be arranged in a hook shape.