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If the baseball field is new, you won’t need to remove old chalk lines.  In most cases, though, you’ll need to use a shovel to remove the ragged, distorted chalk lines that were laid down previously.  The best shovel will have a straight lip, though a curved or pointed lip shovel will do.  Simply scrape the shovel back and forth across the chalk lines until the chalk is blended into the surrounding clay. Removing old chalk lines will prevent a buildup from forming down the middle of the line. Drive a stake into the ground at the pointed end of the home plate (where the catcher squats).  Tie a string to it and line it up with the edge of the plate that leads to first base.  When you arrive at the rear edge of the base, tie the end to another stake and drive it into the ground. The string will measure 90 feet (27.4 m). Tie another string to the stake you’ve already placed at the pointed corner of home plate.  Draw it parallel to the edge of the plate that leads toward third base.  When you reach the back edge of third base, tie the string to another stake and drive it into the ground. Like the first baseline, the third baseline will measure 90 feet (27.4 m). The inside edge is the edge closest to the pitcher’s mound.  Move in a straight lines from home plate to the two bases. Chalk lines are typically two-inches (5 cm) wide, but you could make the lines four inched (10 cm) wide if you wish.  A wider line will require more chalk, but will increase visibility. If you’re applying chalk to a field that will be used in competitive play, there might be regulations you’ll need to follow regarding the width of the lines, so consult your league handbook for more information. The batter’s boxes are located on either side of the home plate.  A template is like a big cookie cutter in the shape of a batter’s box.  Just line the template up with home base, then apply chalk along the inside of the template. Marking chalk is commonly sold at sporting goods stores in 50-pound bags.  You will not need more than 25 pounds (11 kilograms) of marking chalk to chalk a baseball field. Store marking chalk in a cool, dry place between uses to prevent it from clumping. If the dirt or clay is wet, the chalk settles and clumps together.  Avoid applying chalk immediately after it rains or after the field’s sprinkler system was used. If you chalk the field long before the game begins, players might disturb the chalk lines during warm-ups.  The final chalking should take place between warm-ups and the first pitch.

Summary:
Remove old chalk by scraping it off with a shovel. Connect a string from the home plate to the rear edge of first base. Connect a string from the rear point at home plate to the back of third base. Apply chalk along the inner edges of the strings you’ve laid. Make chalk lines two inches (5 cm) wide. Use a template to chalk out the batter’s boxes. Buy chalk online or at your local sporting goods store. Apply chalk when the ground is dry. Avoid chalking the field too soon before a game.