The flat crush test (1) is a measure of the resistance of the flutes in corrugated board to a crushing force applied perpendicular to the surface of the board under prescribed conditions. The test is satisfactory for single-faced or single wall (double-faced) corrugated board, but not for double-wall or triple-wall corrugated board, because of lateral motion of the central facing or facings. This method is not intended for use in testing complex corrugated structures [for testing such structures see TAPPI Useful Method 810 “Leaning Flute Free (LFF) Flat Crush of Corrugated Board”].