What does it mean to "cross midline"? The body has a midline that falls directly in the center of the body and divides the right and left side of the body. Crossing midline is the ability to spontaneously reach across the body with both arms and legs to perform a task on the other side of the body. Why is crossing midline important? Crossing midline is a crucial component for completion of functional, every day tasks that require use of both hands. Crossing midline is importa