Balk
With a runner on, the pitcher cannot fake the runner out. Break the rule and every runner moves up a base.
What it actually is. A balk is the rulebook stopping the pitcher from lying to the runner. With men on base, the pitcher has to commit: once he starts his motion to the plate he must deliver, if he steps toward a base he must throw there, and from the set he must come to a complete and discernible stop before he goes. Rule 6.02(a) lists more than a dozen specific ways to break that promise, including faking to third and throwing to first, dropping the ball, and pitching while not in contact with the rubber. Every runner is awarded a base. With nobody on, the same illegal move is simply a ball.
What a scout reads off it. Balks come in clusters, not in ones. A pitcher with three in a season is usually being called for the same move over and over: a foot that lands closed, a shoulder that turns before the step, a stop that is not quite a stop. When you see one called, watch the same pitcher's next pickoff attempt and you will usually see what the umpire saw. They also spike whenever a pitcher is learning a slide step, which is why they turn up disproportionately among young starters and among relievers who have just been told to hold runners better.
Where the lines are. It is a rare call. A big-league pitcher goes most seasons with none or one. The single-season record is 16, set by Dave Stewart in 1988, the year the rule on the complete stop was suddenly enforced to the letter and 924 balks were called across the majors, more than double the year before. That season is the best evidence there is that the balk is an enforcement decision as much as a rule.
How it lies to you. The balk is the only penalty in baseball that advances runners for something that happened before a pitch was ever delivered, and it is judged on intent that the umpire has to infer from the pitcher's feet. Two umpires can watch the same move and disagree, which is why it is the call that draws managers out of dugouts more reliably than any other.
At Little League and travel ball. This is the rule that ambushes families moving up. In Little League a runner may not leave the base until the pitch reaches the batter, so there is nothing to hold and the pickoff balk essentially does not exist; what gets called is the pitcher starting and stopping his motion. Move to travel ball on a 50/70 or 60/90 field with leadoffs and the balk becomes the most common new call a twelve-year-old meets, almost always for failing to stop from the set or for stepping toward home and throwing to first. Most youth associations, USSSA included, give a warning first at the younger ages and stop warning as the age groups climb.
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