Janome Even Feed Foot - Category B is sometimes referred to as the walking foot, is built-in feed dogs (teeth) that grip and advance the upper layer of fabric whilst working in unison with the sewing machine feed dogs as they grip the underside of the fabric. This action helps to prevent layers of fabric from ?shifting apart? as they move through the machine and eliminates the problem of the under layer of fabric coming up short. The even feed foot is also great for topstitching, which can be spoilt due to irregularity of stitching. This is often caused by the bulk created with the seam allowance especially around collars and reveres. Using the walking foot for topstitching will eliminate this problem and give perfect stitching every time.