The bulger is a driver with the face convexed like a cricket bat, this convex face being thought to prevent a sliced ball, if hit on the heel, flying to the right. By the laws of dynamics, the direction, taken by a ball, depends not only upon the direction from which the impetus comes but also upon the angle at which the face of the club strikes the ball. When, therefore, a ball is hit at such an angle that it is given a left to right spin or is sliced, the spin sends it to the right, and because most golfers who slice a ball generally hit it on the heel, the bulger was devised in order to get the resultant of the two forces and send the ball straight, a bulging face preventing a heeled ball that has been sliced flying to the right.

a - the direction in which the ball will fly when sliced. b - the direction when hit on a convex face without the slice. c - the resultant of the two tendencies when the bulger is used and the ball is sliced.