Can a caliper be used to measure rough or uneven surfaces?

No, it is not recommended. Calipers are designed for measuring smooth, flat, or cylindrical surfaces with good finish. Measuring rough or uneven surfaces will not only result in inaccurate readings (due to uneven contact between the jaws and the surface) but also cause wear to the precision measuring surfaces of the caliper, affecting its long-term accuracy. For rough surfaces, use tools like a micrometer with a spherical measuring head or a dial indicator instead.