Measures the pressure needed to perforate a single paper sheet or paperboard to indicate its load carrying capacity under specific conditions. It has only limited reliability for double-walled, or two-ply corrugated sheets, It is not suited at all for triple-walled, three-ply corrugated sheets. In 1887 J. W. Mullen invented this a requirement in the US shipping container classification scheme. Also known as the Mullen test. Refer to edge crush test.