Abstract: A structural element made of a high impact sheet material, a resilient, semi-flexible core material, and a plurality of independent, preformed parallely-spaced rib members extending substantially across the width of said sheet material and fixedly attached thereto by an adhesive with said sheet material being flat, said plurality of rib members having adjacent, confronting side surfaces substantially parallel to one another, the forces created by bending of the structural element producing fractional detachment between at least some of said rib members and said sheet material being controlled by the width and height of said rib members and the distance between adjacent rib members and thereby determining the limit of bending of said structural element, thereby enabling a smooth surface of said high impact sheet material by preventing ripples and ridge lines therein with the bending of said structural element.