What tool is used to check the flushness of the manufactured head and driven head of the rivet?

The correct tool for checking the flushness of the manufactured head and driven head of the rivet is a gap inspection shim. This tool is specifically designed to evaluate the consistency of surface alignments in assemblies, ensuring that rivet heads are flush with the surface material.

Using a gap inspection shim, a mechanic can effectively determine whether there are any gaps between the rivet heads and the material they are attached to. If there's a gap, it may indicate an issue with the riveting process that needs to be corrected to maintain structural integrity and aerodynamics in aerospace applications.

While other tools like calipers, rulers, and micrometers are useful for measuring dimensions and thicknesses, they do not serve the specific purpose of checking flushness in the way a gap inspection shim does. Calipers and micrometers measure specific dimensions, but they do not provide the necessary tactile feel or precise gap evaluation needed for assessing flushness. Therefore, the gap inspection shim is the most suitable tool for ensuring that rivet heads are properly flush, which is critical in aerospace assembly for safety and performance.