Why do umpires indicate whether a caught fly ball is fair or foul?

Question

If a batter pops up or flies out down a base line, and the fielder catching the ball is within a couple feet of the foul line, the umpire will always signal the out, and then "fair" or "foul" depending on where the ball is caught.

Why is this? Runners can tag up on either a foul or fair ball. A missed play would likely be scored an error on the fielder regardless of which side of the line the ball dropped.

I know there's a (slightly) different scoring notation for caught fair and foul balls. If the left-fielder catches the ball in fair territory it's scored ("7" or "F7"); in foul territory ("7F" or "F7F"). Is there any reason to indicate fair or foul here other than as a courtesy to the scorer to inform him that he needs to write an extra letter?

Answer 1

Lets say there are no outs and a runner on 3rd, and a ball is hit to the right fielder who dives for it near the foul line. The ball is still in fair territory when the player dives for the ball, but as he lands, the ball falls out of his glove in foul territory. The umpire should have made his decision first as to whether the ball was fair/foul (so lets say his call was fair). Then after that the catch/no catch call should be made. So now say the umpire rules it as no catch. Although the ball has been dropped into foul territory, it has already been ruled fair so it is a live ball and the runner at third would have gotten the fair signal allowing him to tag up. The fair/foul call should be made FIRST proceeded by catch/no catch as to avoid any confusion.

So basically the reason is just for assurance purposes (like if the fielder drops the ball)

Hope this helps.

Answer 2

Let's say there's a runner on 3rd with less than 2 outs. The game is tied and it's the bottom of the last inning. A deep flyball is hit towards the RF or LF line. If the fielder catches the ball, he'll have no chance to throw the runner out at the plate. If the umpire signals foul first, the fielder can let it drop, since the play will be dead and the runner can't advance. In this situation, it's clearly important for the fielder to know whether it's fair or foul before he decides whether to catch the ball or not.