Abstract: A rib-engaging support is made from a unitary web having four panels, including two inner panels and two outer panels, with each panel having the shape of an isosceles trapezoid. Each panel includes a base side and a top side parallel to each other, and a pair of equal sides extending between the base side and the top side. The inner panels have a smaller size and are joined together at their bases. The outer panels have a larger size, with their top sides joined to the top sides of respective inner panels along respective fold lines. The web is folded such that the inner panels are folded one on top of the other and the outer panels are folded one on top of the other, with the inner panels on top of the outer panels. A rib-receiving pocket is formed between the inner panels and the outer panels.