Applies to shop or yard work only. Applies to the manufacture of concrete products as a commercial enterprise operated at a permanent location. Not available at a construction site or for any plant established or operated in connection with construction work. Contemplates the manufacture of concrete blocks, poles, piles, beams, sewer pipes, tile, patio blocks, roofing tiles, lawn ornaments, garden furniture, sills, grills, ornamental figures and architectural units, modular homes, coffins, caskets, burial vaults, pre-cast or pre-stressed beams or girders.