VDI, Dusseldorf, Germany, released a guideline providing a summary of hardness testing methods for use on metallic materials. Each individual method and scope is described. The revised VDI/VDE 2616-Part 1 includes references to features of the methods, as well as advantages and disadvantages. Suitable test methods can be selected for specific testing purposes by using integrated charts and diagrams. The guidelines supplement existing standards covering hardness testing on metals. In addition, hardness test methods that are not included in standards are described, provided that they are in widespread practical use.