本程序描述了一种测量盘式制动器摩擦材料蹄片上方任何给定高度处存在的底层（也称为背衬层）分数的方法。测量底层分布有助于计算可用衬里厚度和摩擦材料质量管理。

This procedure describes a method for measuring the fraction of underlayer (also referred to as backing layer) existing at any given height above the a disc brake friction materials shoe plate. Measuring underlayer distribution is useful for computing useable lining thickness and for friction material quality management.