A crochet hook is a tool consisting of a slender handle with a hook at one (or both) ends, which is used to pull thread or yarn through loops to create crochet stitches. Sizes, handles, and materials that make up crochet hooks can vary. Each type has specific benefits and drawbacks from the ease of use, price, and comfort. There are several systems of letters and/or numbers that describe the sizing of crochet hooks. The size of the hook is usually matched with an appropriate ply or thickness of thread. 1) Steel: For the smallest sizes and are often used in fine thread crochet such as in doilies. 2) Aluminum are available a large range of sizes. Aluminum hooks allow you to crochet smoothly and quickly. 3) Plastic: available in all the common sizes as well as jumbo hooks. They are very large and are usually made of hollow plastic, because it is lightweight. 4) Bamboo: lightweight and warm in the hand and are available in all but the smallest and jumbo sizes. 5) Tunisian: longer than regular hooks, and sometimes have a hook on each end. A crochet hook with a hook on both ends is also called a cro hook. Like a knitting needle, you keep your stitches on a tunisian crochet hook as you create the fabric. Tunisian crochet is also called afghan crochet, and the fabric looks different from normal crochet, and a little like knitting.