The NCAA rulebook indicates that a checked swing shall be called a strike “if the barrel head of the bat crosses the front edge of home plate or the batter's front hip.” That is pretty simple and straightforward language, however, not particularly easy to distinguish.

How do you tell if a check swing is a strike?

To indicate a checked swing, the umpire will make a "safe" gesture with their hands; to indicate a full swing, they will clench their fist. If a ball that passes the batter goes through the strike zone, it is a strike even if a swing is checked.

What is considered a swinging strike?

The “Swinging Strike” Mechanic is used by the Plate Umpire when calling balls and strikes, specifically on a strike in which the batter swings and doesn't make contact with the ball.