① Make the base line: make a rectangle with a back length of 37cm and a width of B/2+5 (relaxation) = 46cm. The left line of the rectangle is the back center line, and the right line is the front center line. The upper line is the basic line, and the lower line is the waist auxiliary line

②Basic dividing line: measure B/6+7=20.7cm from the end point of the back midline, and draw a horizontal line from this point to the front midline. This line is the armhole deep line, also called the bust line.

③Straight line of side seam (straight line of swing seam): Take the 1/Z point down on the deep line of the armhole and make a vertical line to intersect the auxiliary line of the waist. This line is the dividing line of the front and back pieces.

④Back width line and chest width line: On the deep line of the armhole, measure B/6+4.5=18.2cm from the rear midline to the right and B/6+3=16 from the front centerline to the left. 7cm fixed point, draw a vertical line upwards and cross the upper basic line respectively, and draw the back width line and the chest width line.

⑤Back neckline arc: Measure B/Z0+2.9=7cm from the end of the back center line to the back neck width. Divide the back collar width into 3 parts, measure 1/3 of the back collar width at the back collar width point upwards = 2. 3cm is the back collar depth (the back neck side point), draw the back collar line arc with a smooth arc line.

⑥ Back shoulder oblique line: Measure down from the intersection of the back width line and the basic line to take 1/3 of the back collar width = 2.3cm as a horizontal auxiliary line, and measure 2cm (fixed inch) from the back width line to the back shoulder End point, connect the side point of the back neck and the end point of the back shoulder to complete the back shoulder oblique line. Measure the length of the back shoulder diagonal line to 14cm.