By changing the way yarns interlace, and how tightly they are pulled together, the structure of the fabric can be changed. Different fabric properties can be achieved. Most of the fabrics you can buy are soft and flexible. The spaces between the threads allow movement. If these spaces were tightened up, the fabric would stiffen. You can make fabric more flexible in one direction than another by closing up the space between either the warp threads or the weft threads. You can also change the way a fabric stretches by using Lycra or other stretchy yarns in direction