A crochet hook is a tool used in the craft of crochet, which involves creating fabric from yarn. It typically has a long, slender shaft with a hook at one end, allowing the user to pull yarn through loops to form stitches. Crochet hooks come in various sizes and materials, including aluminum, plastic, and wood, catering to different yarn types and project needs. The size of a crochet hook is usually indicated by a number or letter, which corresponds to the diameter of the hook. Using the right size is important for achieving the desired tension and appearance in a finished piece. Crochet hooks can also have ergonomic designs to enhance comfort during extended use.