What shims are used under the wheels during straight edge calibration?

Shims are critical in the process of straight edge calibration to ensure accurate measurements. The specific shims used, which in this case are 3/16 and 3/8, provide a precise means of creating a level reference point along the straight edge. This calibration is essential for determining flatness and ensuring the quality of pavement is maintained during the asphalt paving process.

Using these particular shim sizes helps in achieving the necessary gauge when verifying that the surface is within tolerances specified by guidelines or regulations. By having shims that are close in size but still distinct, it allows for a more fine-tuned adjustment during calibration, minimizing potential errors in readings due to surface irregularities or variations that may exist in the material or application methods.

The other options do not provide the most effective or traditionally accepted sizes used for this specific calibration task, which are essential for creating a reliable and consistent measurement standard in asphalt paving practices.