The Shore Scleroscope measures hardness in terms of material elasticity. A diamond-tipped hammer (size of 40 grains; 2.59 g; 0.0914 oz) is used to strike the testing surface from a known height (10 inches; 254 mm). The rebound of the hammer is measured. The harder the material, the higher the rebound.
Note that the hammer rebound is also affected by other factors, such as the smoothness of the test surface, and the mass, depth, and contour of the specimen.