thick sections by providing a relatively thin sheet and folding over portions of the thin sheet in the areas which ultimately form the corrugation peaks and corrugation troughs so that the latter are defined by a plurality of staked sheet layers application_number US 17632880 A description referring first to fig1 a corrugated plate 2 constructed in accordance with the present invention generally comprises longitudinally extending parallel side by side corrugations 4 which have a generally trapezoidal cross section the corrugations are defined by alternating longitudinally extending and parallel corrugation peaks 6 and corrugation troughs 8 each of which has an elongated essentially flat and relatively narrow crown section 10 of a thickness 34 t 34 which extends over the length of the respective peak or trough angularly inclined or slanted corrugation sides 14 have a thickness 34 t 34 and each of them interconnects a corrugation peak with an adjacent corrugation trough a curved corrugation segment 14 extends over the length of the corrugations and forms the connection between lateral edges 16 of the crown sections and the corrugation sides as is apparent from fig1 34 t 34 is larger than 34 t 34 in other words the corrugation sides are relatively thin while the crown sections of the corrugation peaks and troughs are relatively thick although the benefits of the present invention are attained irrespective of the ratio between 34 t 34 and 34 t 34 it is preferred that the ratio is at least 2 1 and preferably 3 1 or.