This instrument is used for calibration and routine tests of Schmidt hammer. Sclerometers should be periodically tested in order to ensure their proper functioning. The anvil is made of special cast steel. The test consists in determining surface hardness of concrete by measuring the rebound of the weight that hits concrete. In Schmidt hammer type N this weights hits concrete with the energy of 0.225 kG/m (approx. 2.2 N/m). The rebound value (L) can be read directly on the hammer’s scale.