Twill Fabric is technically a double sided fabric a front side and a back side, front side of a twill fabric is the face side and the back side is called the back face,
The face side has a more pronounced wale, very durable and more attractive widely used in the fashion trade, twills are often used for sturdy workwear, school uniforms, corporate wear, general clothing and for durable upholstery, the uneven surface of twill the fabric is a good feature to repel Soiling and staining.
Example of a twill weave in everyday use is denim, if you look closely at any denim fabric you will see the diagonal twill weave.
Twill fabrics technically have a front and a back side, unlike plain weave, whose two sides are the same. The front side of the twill is called the technical face and the back the technical back. The technical face side of a twill weave fabric is the side with the most pronounced wale; it is usually more durable and more attractive, is most often used as the fashion side of the fabric, and is the side visible during weaving. If there are warp floats on the technical face (i.e. if the warp crosses over two or more wefts), there will be filling floats (the weft will cross over two or more warps) on the technical back. If the twill wale goes up to the right on one side, it will go up to the left on the other side. Twill fabrics have no “up” and “down” as they are woven.
Sheer fabrics are seldom made with a twill weave. Because a twill surface already has interesting texture and design, printed twills (where a design is printed on the cloth) are much less common than printed plain weaves. When twills are printed, this is typically done on lightweight fabrics.
Soiling and stains are less noticeable on the uneven surface of twills than on a smooth surface, such as plain weaves, and as a result twills are often used for sturdy work clothing and for durable upholstery. Denim, for example, is a twill.
The fewer interlacings in twills as compared to other weaves allow the yarns to move more freely, and therefore they are softer and more pliable, and drape better than plain-weave textiles. Twills also recover from creasing better than plain-weave fabrics do. When there are fewer interlacings, the yarns can be packed closer together to produce high-count fabrics. With higher counts, including high-count twills, the fabric is more durable, and is air- and water-resistant.
Twills can be divided into even-sided and warp-faced. Even-sided twills include foulard or surah, herringbone, houndstooth, serge, sharkskin, and twill flannel. Warp-faced twills include cavalry twill, chino, covert, denim, drill, fancy twill, gabardine, and lining twill.