A high strength low density multi-purpose panel. The preferred panel is made of a plurality of sections, organized into rows and columns, and each preferably including two voids. The voids are preferably triangular in cross-section and may be rounded at their apex and corners. Solid strips of material, extending between opposite corners and between the faces of each section, intersect at the center of each face, resulting in an X-shaped cross in each section. Each section is rotated ninety degrees with respect to each adjacent section. Each section shares sides with four adjacent sections and corners with four cater-corned sections. The common sides create perpendicular sets of parallel braces running the panel's length and width. The shared corners align and join the X-shaped cross braces with the X-shaped cross braces of their cater-cornered neighbors, creating diagonal braces that run across the entire panel.