is this the thing that looks sort of like a huge "C" clamp.....and has little wheels that roll along the inside and outside of the tire rim.....some sort of gears that keep a grease pencil in the center of the two little wheels, and you "roll" it around the tire and the grease pencil leaves a line down the center of the tire tread ?.............never seen one before.....
naa, i might just know where one is at
No, it was a spring loaded metal rod with point on the end. You would wind it around against the spring and set it up underneath the tire with the tire jacked up on the alignment rack. Then you would just spin the tire around and it would score the tire. But I am sure there are other such devices that might us a grease pencil.