Abstract: A translucent block includes a pair of parallel upper and lower surfaces each having a generally pentagonal shape. There are a pair of generally rectangular, nonparallel side faces whose planes intersect to form a dihedral angle at 45.degree.. A generally rectangular first opposing end wall is joined to the upper and lower surfaces and is perpendicular therewith, and is joined to the side faces proximal to the vertex of the 45.degree. dihedral angle. A second opposing end wall is formed of two equal sections joined at an obtuse angle to each other. The vertex of the obtuse angle points away from the first end wall, and the sections of the second end wall are perpendicular to and are joined to the upper and lower surfaces of the block and are joined to the nonparallel side surfaces of the block distal from the 45.degree. dihedral angle. The translucent block can be joined to similar translucent blocks and/or different translucent blocks to form a wide variety of wall structures of 45.degree.