Less than an inch can alter the course of history in Major League Baseball. It is imperative that field dimensions are exact and that umpires have a clearly defined boundary to determine whether a ball is fair or foul.
Have you ever wondered how a Major League Baseball grounds crew manages to lay down perfect foul lines and batters boxes before every game? In the Giants' case, they use an old-school, box chalking system. Nowadays, not all ballparks use real chalk to lay down the surface lines. Some grounds crew choose to use a spray paint can mounted to a push cart.
In this video, Giants manager of field operations Jeff Winsor provides a detailed, behind-the-scenes look at the precise chalking process at AT&T Park.
How do big league grounds crews get it right every day? The key is having home plate in the exact same spot for every game. Using the apex of the plate, they can accurately determine where each base and the rubber of the pitcher's mound should be.
Proper Distance From Home Plate:
Second Base: 127 feet, 3-3/8 inches
First Base: 90 feet
Third Base: 90 feet
Pitcher's rubber on the mound: 60 feet, 6 inches
It should be noted that most grounds crews don't actually have to measure these distances daily. They have holes in the infield that they simply plug the bases into.