[Wikipedia excerpt: ‘….Ceramic materials for ‘T’ include earthenware, stoneware and porcelain. Terracotta is a traditional material used for roof ‘T’ …. ‘T’ are thin objects, usually square or rectangular in shape. A ‘T’ is a manufactured piece of hard-wearing material such as ceramic, stone, metal, baked clay, or even glass, generally used for covering roofs, floors, walls, or other objects such as tabletops. Alternatively, ‘T’ can sometimes refer to similar units made from lightweight materials such as perlite, wood, and mineral wool, typically used for wall and ceiling applications. In another sense, a ‘T’ is a construction tile or similar object, such as rectangular counters used in playing games (see tile-based game). The word is derived from the French word tuile, which is, in turn, from the Latin word tegula, meaning a roof tile composed of fired clay.
‘T’ are often used to form wall and floor coverings, and can range from simple square ‘T’ to complex or mosaics. ‘T’ are most often made of ceramic, typically glazed for internal uses and unglazed for roofing, but other materials are also commonly used, such as glass, cork, concrete and other composite materials, and stone. Tiling stone is typically marble, onyx, granite or slate. Thinner ‘T’ can be used on walls than on floors, which require more durable surfaces that will resist impacts. These are commonly made of ceramic or stone, although recent technological advances have resulted in rubber or glass ‘T’ for floors as well. Ceramic ‘T’ may be painted and glazed. Small mosaic ‘T’ may be laid in various patterns. Floor ‘T’ are typically set into mortar consisting of sand, cement and often a latex additive. The spaces between the tiles are commonly filled with sanded or unsanded floor grout, but traditionally mortar was used..….’]