Hardness testing of metals is conducted so that one may correlate the results with another material property of interest, such as tensile strength or resistance to abrasion. Too soft, and a material may not be strong enough for its intended purpose. Too hard, and it may be brittle and subject to cracking. A wide variety of different physical methods and instruments are available to determine hardness, but there is no single best test method and no single best tester. Instead, the solutions depend on the object to be tested.