This practice covers the determination of indentation hardness of metallic materials using comparison hardness testers. This practice applies only to those comparison hardness testers, normally portable, that use standardized test blocks in accordance with Test Method E10 as a basis for comparison. Calibration of comparative test bars (rods), used for comparison to determine hardness numbers, is also covered by this practice. The indenting force used during comparison hardness testing is normally an impact load applied by striking a hammer at the appropriate areas as outlined in the manufacturer's instructions. Final indentation diameter in both the comparative test bar and material tested shall be within the range of the comparator used for the instrument.This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.