A ___________ is used to inspect rivet head gap.

A gap inspection shim is specifically designed to measure the gap between rivet heads and their respective surfaces. This tool is crucial in aerospace assembly, as proper rivet head contact is essential for structural integrity and the overall strength of the assembly. The shim allows a technician to assess whether the rivet is properly seated and if the gap falls within acceptable tolerances, ensuring that the rivet connection meets the engineering specifications.

Other tools listed do have their uses in various measuring tasks; however, they are not tailored for inspecting rivet head gaps. A caliper is more suited for measuring dimensions and thicknesses, while a rivet gauge provides comparative measurements but does not specifically address gap inspection. A measuring tape is generally used for longer lengths rather than the fine measurements involved in gap inspection. Thus, the gap inspection shim stands out as the best tool for this particular need in the aerospace industry.