Sheet metal panel

A roll formed sheet metal panel formed of strip sheet metal cut to a predetermined length, said panel comprising;

• a central portion and two side portions;
• continuous roll formed longitudinal fold formations extending continuously along both side portions of said panel running from one end to the other thereof without interruption;
• a plurality of identical transverse ridges and indentations of continuous sinusoidal shape in elevation formed in the central portion of said panel, along a length less than the length of said panel, and extending from side to side of said central portion between said longitudinal fold formations, and terminating just short of said longitudinal fold formations;
• flat planar junction portions of said central portion at each end of said panel extending from side to side of said central portion between said longitudinal fold formations wherein said transverse ridges and indentations are absent, and being flanked by said longitudinal fold formations on either side thereof, said transverse ridges and indentations having upper and lower extremities, the lower extremities of said indentations lying in a common plane with a plane containing said planar junction portions, and said indentations extending to one side only of said plane, and exhibiting compound concave and convex curved contours characterized by an absence of flat sections and sharp angles, and complementary continuous lengthwise mating formations formed in said longitudinal fold formations, whereby said panels may be interlocked in edge to edge relation to form a structure.