A tool designed for tightening or loosening nuts requires precise engagement with the nut’s facets. The measurement across the hexagonal or other polygonal cross-section of the tool’s working end, expressed in millimeters, determines this crucial fit. For example, a 5 mm measurement indicates the tool is designed for nuts with a 5 mm distance across opposing flats.
Accurate measurement ensures a secure grip, preventing slippage and potential damage to the nut or the tool. This precision is particularly critical in applications with tight tolerances, such as electronics assembly or automotive repair. Historically, standardization of these measurements simplified tool selection and improved interchangeability, increasing efficiency in various industries.