Abstract: A panel of spaced, parallel, translucent, outer sheets of set plastic material with an inner sheet of corrugated sheet plastic disposed therebetween with the crests of the corrugations at the opposite faces of the corrugated sheet being engaged with, and secured in fixed relation to, adjacent outer sheets, respectively. Each corrugation has alternate show areas and shade areas. The show areas are coated with material which reflects light or impedes the passage of light therethrough. The shade areas are generally uncoated so that, relative to the show areas, their reflectivity is less and their light transmission is greater. The corrugations are so related to the outer sheets that, in the panel cross section, they define with the outer sheets right angle triangles with one side of each corrugation at a right angle to both outer sheets. The resultant panel is thus a truss structure, having high strength, desirable controlled light transmitting characteristics, and high heat insulating properties.