Specifies the method of Knoop hardness test covering test forces up to and including 9,807 N. The principle of the method is forcing a diamond indenter, in the form of a rhombic-based pyramid with specified angles between opposite faces at the vertex, into the surface of a test piece and measuring the long diagonal of the indentation left in the surface after removal of the test force. The Knoop hardness is proportional to the quotient obtained by dividing the test force by the projected area of the indentation.