Knoop Hardness Scale
The Knoop hardness scale is one way in which the hardness of a material is represented numerically. Hardness is the resistance of a material to indentation and is measured by the permanent depth of an indentation that has occurred. The Knoop hardness scale can be tested using similar methods to the Brinell harndess scale. However, the Knoop hardness scale uses an indenter that is shaped like a rhombus and is particularly useful for small, thin, or delicate materials that require a force load of 1kgf or less.