The delivery of a curveball is entirely different from that of most other pitches. The pitcher at the top of the throwing arc will snap the arm and wrist in a downward motion. The ball first leaves contact with the thumb and tumbles over the index finger thus imparting the forward or "top-spin" characteristic of a curveball. The result is the exact opposite pitch of the four-seam fastball's backspin, but with all four seams rotating in the direction of the flight path with forward-spin, with the axis of rotation perpendicular to the intended flight path, much like a reel mower or a bowling ball.