The darning foot is for mending fabrics that have rips or holes in it. It is best if you use a special darning stitch on your sewing machine. It is so fast and easy. The foot actually moves up and down with the needle to make sure you encompass entirely all the parts of the fabric you are darning under your stitching. You select your start point and start sewing forward, then stop and hit the reverse button and hold the foot peddle down. You will finish sewing out multiple passes back and forth parallel to each other, then it will go back on top across the beginning stitching perpendicular to that of the first stitching.