Adjustable magnetic seam guide that attaches to the metal needle plate to guide fabric edges for straight, uniform seams. Slide to the desired allowance to support topstitching and long seams, then remove when not in use. Ideal for beginners and production runs where repeatable accuracy matters. Do not use on computerized machines to avoid potential magnetic interference. For best results, test on a scrap first and match tools to fabric weight and machine class for consistent results.