ASA Double Base - Purpose of 8.2.M.4.?

[jimpiano]

Maybe it is helpful to look at the double base rule.

It was adopted to prevent collisions and injuries on the play at first base. The batter-runner is the only offensive player required to use the colored portion of the double bag. The play is a force out, since the batter/runner need not be tagged; the batter/runner is out unless he/she gets to the base before the ball. If the batter/runner misses the colored portion or touches only the white portion and is tagged out before returning to the white or colored portion the batter/runner is out. This would be a live appeal. Rule 8 -2, m 3

So once the batter/runner reaches first base the requirement of using the colored portion is removed. 8-2, m6,7,8

If the batter/runner interferes with the fielder by using only the white portion the batter/runner is out 8-2,m9

In most cases the play at first base to attempt to put out the batter/runner involves the fielder in fair territory with the runner using the portion of the double bag in foul territory. But sometimes the play can cause the fielder to use foul territory so the rulesmakers allow the fielder and the batter/runner to switch use of the double base to prevent collisions.

You asked the reason for 8-2,m 4---that is the reason.

Similarly 8-2, m 5 allows the same choices on a throw that forces the fielder to the foul side of first base.

In any event the words force play describe how the out is made at first base.