he was measuring the width. Plastigage is a precision metered clay rope that comes in different measurment ranges. By laying it across the crank journal and torquing down the caps, it flattens out. The amount that it flattenes out, tells the clearance between the bearing shell and the crank journal. Pretty straightforward if you think about it. The closer the clearance, the more it flattens out and the wider it is. comparing the width to the reference numbers on the package, tells the clearance.
