What tool is commonly used to adjust treadmill elevation calibration?

The carpenter's level is an essential tool for calibrating treadmill elevation due to its ability to ensure that the surface of the treadmill is perfectly horizontal or inclined at the correct angle. When adjusting the elevation of a treadmill, it is crucial to determine whether the surface is level before making precise adjustments. A carpenter's level provides a clear visual indication of any deviations, allowing for adjustments that ensure the treadmill provides the intended gradient for effective exercise training.

Other tools such as a ruler or measuring tape might not offer the same level of precision for leveling, as they measure distance rather than indicating whether a surface is flat or inclined. Similarly, while a laser level can be very accurate, it is less commonly used in practical settings like treadmill calibration, where the straightforward functionality of a carpenter's level is often sufficient and more user-friendly. Thus, the carpenter's level is the most common and effective tool for this specific calibration task.