[header] How to throw a cut fastball [title] Start off by gripping the ball as you would a two-seam fastball. [step] A two-seam fastball is gripped with the index and middle fingers on the two narrow seams of the baseball. [title] Instead of leaving your fingers there, move your two fingers over to the right. 
[step] Make sure your fingers are relatively close together. Your fingers can either be positioned so that your middle finger runs along the seam, or so that the seam runs directly in the middle of both fingers.