Get your body into a position where it looks like an inverted V, legs straight and back straight, hands pointed forward, and then lower your head down between your hands, elbows out to the side, and press back to starting position. Your head should be in-line with your back. Don't look down at the floor.
It primarily works your shoulders and triceps but will also involve some chest activation and core stabilizers. It is similar to what you are working with a handstand push-up but with only some of your body weight.