String a tennis racket. Take a look at this instructional video and learn how to lace your mains for a two-piece string job for your tennis racket. To find out where you start is by counting how many grommets you have on your racket. By dividing the number by two, you can determine where to start, top or bottom. If the number you yield is odd, you start from the bottom. If the number you yield is even, you start from the top.