These three rules were added to modern baseball to prevent the defense from mishandling the ball (intentionally or unintentionally) and then allowing them to turn easily a double-play:
-Intentionally dropped ball: An intentionally dropped ball is when an infielder intentionally drops a fair line drive, pop up, or bunt with at least first base occupied and less than two out. The batter is out immediately, the ball is dead immediately, and runners must return to their bases at the time of the pitch (NF 5-1-1j and 8-4-1c). The following situations can not be an intentionally dropped ball: a fly ball to the outfield, a foul ball, a pop up with 2 outs, and a line drive with runners on second and third.
- An infield fly: An infield fly occurs on a fair ball (but not a line drive or a bunt) with less than two outs and at least 1st and 2nd occupied. The batter is out and the ball remains live, regardless of wether the ball is caught or dropped. An intentionally dropped infield flight remains live. Runners advance at their own risk. A runner hit by an infield fly is handled like other runners struck with a batted ball (with the unique exception that a runner on a base that is hit by an infield fly is protected, unless he intentionally interferes): NF 2-10
- A third strike not caught by the catcher when 1st base is occupied before there are two outs. In this case, the batter is immediately out and the ball remains live: NF 2-24-3. Runners advance at their own risk. A ball that hits the ground (before or after it crosses the plate) is uncaught.