What type of gauge should be used to inspect the hole at four places within the measurement zone?

The correct gauge type to use for inspecting a hole at four places within the measurement zone is the Federal gauge. This type of gauge is typically used in precision measurement and inspection tasks, particularly in aerospace applications, where accuracy and reliability are paramount. Federal gauges represent a set of standard measurements that help ensure consistency across different parts and processes.

Using a Federal gauge provides the advantage of adhering to established specifications and tolerances, thereby supporting compliance with industry standards. This precision is necessary in the aerospace field, as even small deviations can lead to significant safety and performance issues. By examining the hole at multiple locations with a Federal gauge, mechanics can accurately assess its uniformity and integrity, ensuring that it meets the required design specifications for both functionality and safety.

In contrast, other gauge types like metric, standard, or inch may not provide the degree of accuracy or standardization needed for such critical applications. Each of these options may be suitable in different contexts, but for aerospace assembly where precision is crucial, the Federal gauge stands out as the most appropriate choice.