GB/T 457-2008 "Determination of Folding Endurance of Paper and Board" specifies two test methods, the Schopper method and the MIT method, and clarifies the conditions and precautions for instrument use. The Schopper method is applicable to paper with a thickness of less than 0.25 mm and a tensile strength greater than 1.33 kN/m, as well as paperboard with a thickness ranging from 0.25 mm to 1.4 mm. The MIT method, with its adjustable spacing clamps, is suitable for paper and paperboard with a thickness not exceeding 1.25 mm, providing a standardized basis for evaluating the ability of paper and paperboard to withstand repeated folding.