This standard specifies the method of verification of testing machines for determining Knoop hardness for metallic materials in accordance with EN ISO 4545. It covers test forces from 0,098 07 N to 9,807 N. The method is recommended only for indentations with diagonals greater than or equal to 0,020 mm. This International Standard describes a direct verification method for checking the main functions of the machine, and an indirect verification method suitable for the overall checking of the machine.