The bony protrusion in the middle of the human frontal bone. The forehead keel refers to the bony protrusion in the middle of the human body's frontal bone, also known as the frontal tubercle or frontal protuberance. Located in the center of the forehead, it is a raised structure formed by the frontal bones. The shape and size of the forehead keel varies between individuals. It shows a slight arc and semicircle, gradually tapering toward the top of the head. Some people's forehead keel is more obvious and more prominent, while others are less obviously flat.