What tool is used to check the twist of a connection rod?

The twist of a connection rod is typically checked using a thickness gauge. This tool is designed to measure the thickness of materials, which can help identify any distortions or twists in the rod. When assessing the twist, the thickness gauge can provide a direct measurement of the rod's dimensions at various points, allowing for the detection of any discrepancies that might indicate a twist.

The other tools mentioned, such as a caliper gauge, depth gauge, and micrometer, are more specialized for different types of measurements, like lengths or depths, rather than specifically identifying twisting. A caliper gauge is primarily used to measure internal, external dimensions, and depths. A depth gauge measures the depth of holes or slots, while a micrometer offers precise measurements of small dimensions but does not focus on assessing twist or distortion directly. Therefore, a thickness gauge is the most appropriate tool for checking the twist of a connection rod.