This specification covers structural clay load-bearing facing tile and facing brick and other "solid masonry units" made from clay, shale, fire-clay, or mixtures thereof, with or without the addition of grog or other mixtures, having a finish consisting of a ceramic glaze fused to the body at above a certain temperature making them inseparable, excluding natural salt-glazed ware. The following grades and types are covered: Grade S which is for use with comparatively narrow mortar joints, Grade SS which is for use where variation of face dimension must be very small, Type I or single-faced unit which is for general use where only one finished face will be exposed, and Type II or two-faced unit which is for general use where two opposite finished faces will be exposed. The brick and tile are manufactured from clay, shale, or similar naturally occurring substances and subjected to a heat treatment at elevated temperatures (firing). The heat treatment must develop sufficient fired bond between the particulate constituents to provide the strength requirements specified. The masonry units are classified as solid masonry unit and hollow masonry unit. The former is a unit whose net cross-sectional area in every plane parallel to the bearing surface is 75 % or more of its gross cross-sectional area measured in the same plane and the latter is a unit whose net cross-sectional area in any plane parallel to the bearing surface is less than 75 % of its gross cross-sectional area measured in the same plane. Different tests shall be performed in order to determine the following properties: compressive strength, imperviousness, opacity, resistance to fading, resistance to autoclave crazing, flame spread, fuel contribution, smoke density, toxic fumes, hardness, and abrasion resistance.