Interference calls are a mixed bag. They don’t happen very often, but they are really not all that hard to call.
Check out this example:

The ball is “clubbed” about 3 inches in front of the plate. The ball stuck in a manner than would make a pro golfer proud. Important for this play is that the ball is in fair territory.
The batter then makes contact with the ball before a fielder does. That my friends is an out.
Rule 6.05(g)
6.05 A batter is out when—
(g) His fair ball touches him before touching a fielder. If the batter is in a legal position in the batter’s box, see Rule 6.03, and, in the umpire’s judgment, there was no intention to interfere with the course of the ball, a batted ball that strikes the batter or his bat shall be ruled a foul ball;
Notice the rule does have an exception. If a batter whacks a ball off his leg while still in the batter’s box – it is a foul ball. This has to written in because a portion of the batter’s boxes are actually in fair territory.
So what is a legal position in the batter’s box?
6.03 The batter’s legal position shall be with both feet within the batter’s box.
Both feet have to be on the ground in the box. In this play, the batter steps on the ball with his foot outside the box. Batter is correctly called out.
One other note from this play – there is a lot going on. The out was ultimately called by the first base umpire. He had a good look at everything. This is good umpiring practice on plays around the plate. The corner umpires will often have a better look at balls off feet, hit batsmen, or catcher’s interference.
RuleGraphics contains information on this and other tricky plays. It is a new way to think about baseball rules. This rule is covered on page 39. See sample on our website.