cross section the ribs 2 have a corresponding curvature to present an enlargement of the strip in profile the ribs are not necessarily spaced uniformly along the length of the reinforcement members as shown in fig1 the reinforcement member a8 has portions 21 wherein the ribs are spaced closely together and a portion 22 that is devoid of ribs the end 12 has a smooth surface for connection with tabs projecting from the panel 8 in the same manner as shown in fig4 various arrangements may be provided for the attachment and of the reinforcement members as shown in fig1 a plate 23 having a greater thickness than that of the band 1 is secured at the end of the band a central hole 16 is provided in the plate 23 for attachment to the tabs of a panel member the plate 23 preferably is secured to the band 1 by beads of welding 24 bonded by an adhesive in fig1 the reinforcement element a1 has an end portion 12 with a central hole 16 a reinforcement plate 26 is secured to the end 12 by welds 27 or bonded by an adhesive the hole 16 in the plate 26 is aligned with the corresponding hold in the end portion 12 in the embodiment of fig2 and 21 the end 12 of the reinforcement member a1 is reinforced by two discs 28 on opposite sides of the strip preferably the discs 28 have an angular boss 29 which is received in corresponding grooves in the end.