Both the front and the back neckline has been piped. You have overlocked the edge of the back piece and topstitched 0.2 cm from the edge.

  • Sew the shoulder seam right sides together
  • Overlock the shoulder and neckline seam in one
  • Press the seam allowances and sew, using  a zipper foot, 0.2 cm from the piping from one side of the shoulder to the othe