Why do we need a straight stitch foot? The straight stitch foot is often used on very fine or very heavy fabrics. This particular foot is flat on the underside to provide an even pressure against the feed dogs and it has a rounded needle hole which offers the benefit of more support around the needle to prevent skipped stitches and puckering.
The Janome straight stitch foot is designed with single hole to allow sewist to sew a straight stitch on lightweight fabrics without skipping stitches.