[SoGARef]

I think I can beat Rut on the shortest English version of the PSK foul enforcement.

For a post-scrimmage kick enforcement to apply all of the following conditions must be met.

1) The foul is by R beyond the expanded neutral zone;

2) The foul takes place during the interval between the snap and the end of a scrimmage kick (not a try) that crosses the expanded neutral zone; and,

3) The ball belongs to R when the down ends.

To answer your other question OAB, the end of a kick is when a player catches or recovers a ball, or the ball becomes dead by rule, such as, going out of bounds. The end of a run is where the ball becomes dead in the runner's possession, or where the runner loses possession if his run is followed by a loose ball, or the spot of the catch when the momentum rule is in effect. The end of the down is when the ball next becomes dead. It is rarely when you blow you whistle. If a down ends in its natural sequence of events it is over before you blow your whistle.