On each of the four corners of the tallit or tzitzit, four woolen spun fringes are drawn through holes in the garment. The fringes now dangle from both sides of the hole, thus becoming eight fringes. These fringes are then coiled and knotted in a prescribed manner, and their ends hang loosely.
When the fringes are originally placed on the corners of the garment, each corner has eight complete strings. If at some point later on some fringes are shortened or torn off, the tallit or tzitzit may be invalid. If indeed the fringes are invalid, it is forbidden to wear this garment until new fringes are attached. As long as each corner contains at least seven complete strings, the tzitzit are still kosher, but the laws become quite complex if any one corner has more than one string which is detached or shortened. In such a situation, the tzitzit should be shown to a rabbi.
Purchasing a Tallit or Tzitzit
"This is my G‑d and I will beautify Him" (Exodus 15:2). We "beautify" G‑d by performing His commandments in a beautiful fashion. This includes spending the extra dollar to purchase high quality tallit and tzitzit. The market today abounds with artfully decorated designer talittot, most of which are halachically acceptable. Many also have the custom of adorning the tallit's headpiece with a silver attarah ("crown").
Because there are many laws involved in the making of a tallit and tzitzit, they should always be purchased from a G‑d-fearing and trustworthy vendor.