Warp and weft are terms for the two basic components used in weaving to turn thread or yarn into fabric. The lengthwise or longitudinal warp yarns are held stationary in tension on a frame or loom while the transverse weft is drawn through and inserted over-and-under the warp. A single thread of the weft crossing the warp is called a pick. Terms vary. Each individual warp thread in a fabric is called a warp end or end. Inventions during the 18th century spurred the Industrial Revolution, Black Siri Interfacing Med Weight Hariform 100% Cotton 58" Pre-Shrinking All interfacings should be preshrunk. Sew-ins can be preshrunk through a press steaming process. Fusible can be preshrunk by immersing in a bowl of very hot (not boiling) water and allowing to sit until the water cools to room temperature. Gently squeeze, then roll in a towel to remove excess moisture and allow to air dry.