The Rockwell scale is used by the metallurgists to specify the hardness of a metal piece. The higher number indicates a harder metal. Different Rockwell hardness scales are used to measure the hardness of different materials. For example, the scale C is used to measure the hardness of knife making steel. It is important to know that the higher level of hardness does not necessarily mean the best metal for an application. In fact, a very hard metal can crack like glass on impact. Manufacturers use a particular alloy in a specific range of hardness rating. The alloy is selected based on the intended use and expected performance. The hardness defined under the Rockwell rating determines the durability and performance characteristics of a metal. This hardness is measured after calculating the indentation depth. A special automatic equipment is used to apply the force and test the metal’s hardness.