For determining the flexural strength and amount of deflection at loads, up to and including maximum load at failure, of rigid insulation boards composed of wood (or other vegetable) fibers of the type generally used for sheathing, insulating, and interior decorative purposes. It is not recommended for evaluation of insulation boards for engineering use, nor for boards greater that 19 mm (3/4 in.) thick, for which the conditions described under Additional Information should be used.