Final answer:
A hardness test measures the rebound height or resilience of a material by dropping a striker from a specific height.
Step-by-step explanation:
In a hardness test, the aspect measured by dropping a striker from a specific height is the rebound height or resilience of the material being tested.
This measurement is related to the elastic properties of the material and can indicate how much energy from the impact the material can absorb without deforming permanently. This kind of test is often used in material science and engineering to determine how a material will stand up to impact forces in practical uses.