[header] How to throw a slider [title] Place your index and middle fingers. [step] Grip the baseball with your index and middle fingers placed tightly together across an outer seam of the ball located at the horseshoe or u-shape seam. For right-handers, place your middle finger across the right half of the seam. 
Left-handers should do the opposite: place your middle finger across the left half of the seam. This should position your fingers towards the outside of the ball (off-center).