Force, accuracy and fluid sequence of body movements are necessary to make full effect of the service. With a service, the server will attempt to achieve a direct point with it via an "ace", or will at least hope to force the opponent into a difficult first hit, thereby affecting the buildup of the opponent's return hit. The ball is hit mostly with the inner surface of the fist, due to control. However, if the server wishes to hit the ball with full force, they will use the edge of a clenched hand. This is called a "hammer hit", and carries greater risk of failure due to the smaller impact surface than the inner surface of the fist.