An overlock is a type of sewing machine that trims the fabric edges while simultaneously stitching them together. It creates a clean, finished edge that prevents fraying, making it ideal for knit fabrics and seams that require stretch. Overlock machines use multiple threads, typically four, to create strong and durable seams. Overlock stitching is commonly used in the garment industry, especially for activewear and stretchy clothing. This technique is also popular among quilters and home sewers for its efficiency and professional finish. Overlock machines can vary in complexity, with some models offering additional features like differential feed for handling various fabric types.