Final answer:
The easiest feature to measure with a vernier caliper is a large distance between outside planes. Cylindrical features can be measured as well, but heights and concave features might present some challenges.
Step-by-step explanation:
When using a vernier caliper, the easiest feature to measure is typically a large distance between outside planes, such as the length or width of an object. Vernier calipers are precision instruments designed for measuring linear dimensions, depths, and diameters to high accuracy. They include two sets of jaws, one for external measurements and one for internal measurements, and a depth rod for depth measurements.
Measuring cylindrical features can also be done with a vernier caliper, but it requires careful placement to avoid errors due to the caliper rocking on the curved surface. Heights from a surface plate might be more challenging to measure with a vernier caliper depending on the overall size and accessibility of the surface. Finally, measuring concave features is often the hardest because it can be difficult to securely position the caliper's jaws on the concave edges.