Ah, I understand what you are referring to now. When setting up the string, I don't use the front wheels at all. Once it is set up using this technique,

"I set a pair of jackstands in front of the car and wrap string around the rear of the car on the rear tires, and set the jackstands in front of the car. I adjust the stands so the string is ever so lightly touching the front sidewall of the rear tires. The string runs parallel to the car terminating at the jackstands positioned at the front of the car".

I measure off from the string to the front and back sidewall of the front tires and adjust the tie rods so that I have 1/8 to 1/16 of toe-in.