This is an excerpt from Softball Skills & Drills - 2nd Edition by Judi Garman & Michelle Gromacki.
A left-handed batter can get a running start before hitting the ball by using the left-side running slap. The lefty is already several steps closer to first. Adding a running start puts tremendous pressure on the defense to make the play quickly. The play often moves the defense out of position as well. To be successful, the batter should have good speed and the ability to put the ball in play.
The batter stands in her standard hitting position so that she does not tip off the defense. The slapper must be in a position where the crossover step will put her on the lines of the front inside corner of the box. To execute the slap, the hitter runs first and hits second. She starts to move when the ball leaves the pitcher's hand. She must not anticipate the release. If she starts too soon, she will have to stop moving to slap the ball or will be way out of the box. The first step is a small jab step with the right foot, either forward or backward. The jab step acts as a timing mechanism. The left foot crosses aggressively over the right foot directly toward the pitcher (see figure 2.6a). The left foot should land on the front line of the box on the inside corner. The right foot then opens slightly toward the pitcher. If the jab step is not used, the first step must include a pivot that opens the hips to the pitcher. The hips are square, but the front shoulder stays closed to permit total plate coverage.
The hands are held close to the body and high in the strike zone on the swing. The front side and front shoulder remain closed. The batter can use a choke grip for good bat control. The bat head is above the hands, which come forward with the crossover step. Both the bat head and the hands are above the ball, and the batter should try to hit the top half of the ball. The batter must be careful not to drop her hands at the start of the swing. She hits the ball as the left foot lands on the front line. The swing is an inside-outside swing. The knob is first, the head of the bat stays back, and the swing is down. The knob and hands stay inside the path of the ball. The hands are out in front. To hit to the left side, the batter should be late with the head of the bat. The batter contacts the ball behind her body and hits down to the ground to put the ball in play.
On the slap follow-through, the batter rolls through the box, being in motion as she hits the ball (see figure 2.6b). She does not need to be moving fast; the important thing is that she is in motion. The slapper continues running toward the pitcher after contact, being careful not to turn early to run to first. On the follow-through, the bat is an extension of the right arm. The batter follows through with the bat in the right hand.