This U.S. industry comprises establishments primarily engaged in manufacturing brick and structural clay tiles. Cross-References. Establishments primarily engaged in-- ? Manufacturing clay fire brick (i.e., refractories)--are classified in U.S. Industry 327124, Clay Refractory Manufacturing; ? Manufacturing nonclay fire brick (i.e., refractories)--are classified in U.S. Industry 327125, Nonclay Refractory Manufacturing; ? Manufacturing glass brick--are classified in Industry 32721, Glass and Glass Product Manufacturing; ? Manufacturing concrete bricks--are classified in U.S. Industry 327331, Concrete Block and Brick Manufacturing; and ? Manufacturing adobe bricks or clay roofing tiles--are classified in U.S. Industry 327123, Other Structural Clay Product Manufacturing.