The handy, portable Zwick Sclerograph hardness testing instrument uses the rebound method and is suitable for determining hardness of steel, non-ferrous metals and rubber. 
 
The Sclerograph is positioned vertically on the specimen and the impact rod is drawn up above the locking device. Pressing the release lever causes the impact rod to fall until the ball strikes the specimen and rebounds. The specially designed locking device holds the impact rod at the highest position after rebound. 
 
By reading off the rebound height and comparing it with the comparison table supplied, the values can be determined in Shore D, Rockwell C and Rockwell B plus Brinell to an accuracy of ± 2 Rockwell units.