Measures the pressure required to puncture a sheet of paper or paperboard as an indicator of its load carrying capacity under specific conditions. It is, however, not suited for triple-walled (three ply) corrugated sheets and has only limited reliability for double-walled (two ply) corrugated sheets. Invented in 1887 by J. W. Mullen, it is a requirement in the US shipping container classification scheme. Also called Mullen test. See also edge crush test.