Which measuring instrument would be least suited for measuring tolerances in complex geometries?

In the context of measuring tolerances in complex geometries, a ruler is least suited for the task due to its inherent limitations. Rulers are typically flat and provide linear measurements along a single dimension. They lack the precision needed for detailed measurements of intricate shapes or features that do not conform to straight lines.

Complex geometries often involve curves, angles, and various three-dimensional profiles that require specialized tools to accurately measure. Instruments like micrometers, vernier calipers, and dial indicators are designed for such precision tasks. For example, micrometers can measure very small dimensions with high accuracy, while vernier calipers can take internal, external, and depth measurements. Dial indicators are particularly useful for measuring slight variations and deviations in surfaces, which can be critical in evaluating complex shapes.

Given these characteristics, a ruler falls short for tasks that demand high precision and adaptability to varying forms, making it the least effective choice for measuring tolerances in complex geometries.