well it could be down with a barbell or dumbell... lie with your back on a bench, your feet on the floor. grasp the bar a little wider than shoulder width with your palms upward, away from your body. slowly lower the barbell behind your head in an arc, keeping your arms straight. pull the bar upwards back to the starting postion.
it looks like a skull crusher except you keep you're elbows in a fixed postion, and bring the weight behind ur brain bucket.