A Go-NoGo gauge refers to an inspection tool used to check a workpiece against its allowed tolerance

Tolerance (engineering)

Engineering tolerance is the permissible limit or limits of variation in# a physical dimension,# a measured value or physical property of a material, manufactured object, system, or service,# other measured values ....

s. Its name derives from its use: the gauge has two tests; the check involves the workpiece having to pass one test (Go) and fail the other (No Go).

It is an integral part of the quality process that is used in the manufacturing

Manufacturing

Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...

 industry to ensure interchangeability of parts between processes, or even between different manufacturers.

A Go NoGo gauge is a measuring tool that does not return a size in the conventional sense, but instead returns a state.