Why do we fold the seam allowance under before cutting corners on garments?

Hi Enasokab

Here is an example for a shoulder seam, explaining why we fold the seam allowance under. This usually has to be done for seams that are sewn first.

After we draft our patterns and we add seam allowances around it, for example at corners to join the seam allowance lines, we fold the shoulder seam line and place the shoulder seam allowance under. Then we put carbon paper right side up under the ends of the shoulder seam to copy the top of the arm whole seam allowance line and top of the neck line seam allowance line for the corners of shoulder seam allowance.

When we cut our garment without using patterns, we take the above notes into consideration. So we need to fold the shoulder seam line and place the seam allowance under to cut the neckline and armhole.

This way, the two ends of the shoulder seam allowance will be flush with the arm whole and neck line seam allowance lines after sewing the shoulder seam line.

Regards
Nehzat