This category contains sites related to the manufacture, supply, and servicing of instruments, devices, and equipment used to ensure the safe, efficient, and effective operation and condition of machinery, machine parts, and a variety of manufactured items. Some sites have a narrow application to an industry or product, but most have a broad range of applicability. In turn, while outside testing is preferred from time to time, the norm is to carry it out on the shop floor, as an attached or integral part of machinery, or through an in-house laboratory. Often enough, too, the testing process forms part of a predictive or preventive maintenance program.