can compress the corrugations to fold the corrugations in the omega u201c t u201d u201c l u201d mushroom or other shape to interlock the layers one advantage of using a rubber compression member is that the corrugations are sufficiently compressed to fold and interlock the layers together but the compressed areas to remain somewhat more flexible than would occur if the compressions are flattened under more extreme pressure alternatively metal plastic wood or other compression members may be used to accomplish the compression of the corrugations to fold and interlock the metal foil layers of the stack together as referred to above in fig4 the longitudinal creases which can be compressed across the corrugations to provide flexibility of the multilayer structure can likewise be formed using any desired method and compression member as will be recognized by one skilled in the art the compression member may be a flat member a v shaped member or a knife edge type member depending on the type of compression and in the case of the longitudinal creases across the corrugations the flexibility desired in the final product the compressed portions of the corrugations to fold and interlock the layers together can be at any.