1, straight seam (double line)-with bottom line design, sewing is more firm; 2. Double stitch (two upper threads and one lower thread) (for straight stitch only): Use double stitch to make the stitch more beautiful and firm. You can sew two parallel straight lines on the cloth at a time. Double thread, double needle and double thread shaft form double thread stitch. (When single seam is needed, it can be replaced by single seam, and double seam can also be normal. )

# Straight seam # Double seam # Double seam # Stitch # Bottom line design # Fabric sewing # Sewing technology