Crochet hooks are tools used in the craft of crocheting, which involves creating fabric from yarn. They come in various sizes and materials, including metal, plastic, and wood. The hook's shape allows it to catch and pull yarn through loops, forming stitches. Crochet hooks are typically measured by their diameter, with larger hooks creating looser stitches and smaller hooks producing tighter ones. Many crocheters choose hooks based on the thickness of the yarn they are using. Some hooks also feature ergonomic designs for added comfort during long crafting sessions.