by UmpSteve » Thu Apr 21, 2011 2:18 pm
To put everything in one answer:
On any play on the batter-runner at first base (albeit not exactly a force play), that BR is required to use the colored bag and the fielder the white bag. If the BR fails to touch the proper bag, it is a live ball appeal that must be made by the defense (same as MISSING the base) by a defensive player in possession of the ball tagging either the base or the runner before that runner returns to first.
If there is no play at first, the batter-runner may touch either base.
On a play coming from the foul side of first (dropped 3K, or booted into foul by defense, even if coming from the outfield), either the defender OR the batter-runner may choose which bag to use. The closeness of play isn't a factor; if play is from fair territory, the bags are assigned, if play is from foul territory, either side can choose either bag (and the running lane then becomes 6', being 3' on either side of the foul line).
If an errant throw from fair territory draws the defensive player off (BOTH bags) and completely in to foul territory, the defense may then use the nearer bag in return to the base. If the errant throw simply takes the defense to the wrong bag, the defense is simply off the base.
Once the batter-runner has passed first base (and is now a runner), either base may be used by both the offense, and defense; it then becomes one double sized base.
As to the second point asking about slappers, the simple fact is that there are no special rules that slappers get different treatment because they choose a different hitting style. The running lane rules apply to all batter-runners that interfere with the defenders opportunity to make a play at first base; and all interference rules apply to slappers out of the batters box if the slapper interferes with a play being attempted by the catcher. That the slapper chooses that hitting style is at risk of violating any other rule, just as a catcher risks causing catcher's obstruction if she chooses to move up into the hitting area between the batter's boxes.