A gnathodynamometer (or occlusometer) is an instrument for measuring the force exerted in closing the mouth. A bimeter gnathodynamometer is one with an adjustable central-bearing point.
As per the inventor's design study, the instrument works well "in measuring maximal bite force and masticatory efficiency of incisor and molar teeth, respectively."
Sharks are baited into biting hard plastic sheets, which are brought to the laboratory. The depth of the indentations shows the force of the bite. The inventor is J. N. Snodgrass.
References
Gnathodynamometer Wikipedia(Text) CC BY-SA