To prevent ridge marks on the surface of the garment left by the seam allowance on straight or curved edges of necklines, collars, and cuffs, the seam allowance is graded by trimming it in layers.

• 为了防止领圈、衣领以及袖口的直边或曲边的缝份在衣服的表面隆起,因此缝份要分层修剪(各层的宽窄修剪得不一样)。