The BOHIN magnetic seam guide helps you sew straighter lines by providing a physical edge to follow as you guide fabric under the presser foot. Place it on the metal needle plate at your chosen distance from the needle to support repeatable seam allowances for piecing, topstitching, and hems. Reposition as needed for different widths, and remove it before storing so it does not attract stray pins or metal shavings in your sewing area.