The Vernier Caliper is a precision instrument that can be used to measure internal and external distances extremely accurately. The Vernier Caliper consists of a main scale fitted with a jaw at one end. Another jaw, containing the vernier scale, moves over the main scale. When the two jaws are in contact, the zero of the main scale and the zero of the Vernier scale should coincide. If both the zeros do not coincide, there will be a positive or negative zero error.
This video explains how to find the volume of a small sphere, cylinder, beaker and a rectangular block by measuring its associated dimensions.