What does a leveling rod measure?

A leveling rod is specifically designed to measure the difference in elevation between two points. It is used in surveying and construction to determine how much higher or lower one point is in relation to another. By aligning the leveling rod with a leveling instrument, the user can read the difference in height, ensuring that construction work such as grading or pouring foundations is done accurately and to specification.

The other options do not pertain to the primary function of a leveling rod. For instance, measuring distance between two points typically involves tapes or measuring wheels, while angle measurements are done with tools like theodolites or protractors. Additionally, while a leveling rod may be used in the context of leveling a foundation, it does not directly measure the level of the foundation itself; rather, it assists in ensuring that the foundation is at the correct elevation.