Base line

From BR Bullpen

The base lines are the sections of the foul lines which extend between home plate and first base and third base. A corridor is demarcated on the outside of the first base line, in which the baserunner must stay while trying to reach first base. The coaches box is also demarcated outside the two base lines.

The rule regarding foul balls differs on whether a ball lands near the base line in the infield or near the foul lines in the outfield.