The Comments to Official Baseball Rule 8.02(c) provide that the manager or catcher may request the plate umpire to ask a partner for help on a half-swing when the plate umpire calls the pitch a ball. The rule further states that appeals on a half-swing may only be made on a call of ball and when asked to appeal.
The preferred mechanic for asking help on a check-swing is for the plate umpire to point assertively with the left arm directly at the appropriate base umpire while asking if the batter swung. This mechanic helps avoid confusion between an appeal and a strike mechanic.
Under the Official Baseball Rules, the plate umpire has an obligation to ask for help when the catcher or manager of the defensive team requests an appeal.
Play (1): Runner on first base, 3-1 count on the batter. Runner is stealing on the pitch, and batter check-swings. Plate umpire rules batter did not swing (ball four), but catcher throws the ball to second base nonetheless, resulting in the runner from first being tagged before such runner reaches second.
Ruling: Umpire at second should initially not rule the runner safe or out since it is ball four—unless appealed and ruled a swing. If an appeal is made and ruled a strike, umpire at second should then make the call of “safe” or “out,” depending upon the initial play at second. (See Official Baseball Rule 8.02(c) Comment.
Play (2): Runner on first base is stealing, three balls on the batter. The next pitch is a check-swing that the plate umpire initially rules a ball. The batter-runner takes off for first base and in so doing interferes (out of the batter’s box) with the catcher’s throw to retire the runner attempting to reach second. Runner is safe at second. An appeal is made to the base umpire regarding the check-swing, and the base umpire rules a swing.
Ruling: Batter’s interference. Batter is declared out and runner returns to first base. Note that if this situation occurred with two strikes on the batter, then both the batter and runner are declared out. (See the last paragraph of Interpretation #66.)
Also note in the Comments to Official Baseball Rule 8.02(c) the important time limitations instituted in 2014 regarding a request for the plate umpire to appeal to the base umpire on a check-swing.