seamlines

Seamlines are the lines along which two pieces of fabric are joined in sewing and garment construction. They indicate where stitches will pass and where fabric pieces should align. In pattern drafting, a seamline corresponds to the edge of a pattern piece that will be sewn to another piece, and it often differs from the true fabric edge to include a seam allowance.

In practice, seamlines guide cutting, matching, and assembly. They must be aligned with the fabric grain and, when patterns include prints or nap, seamlines are positioned to minimize visual disruption or misalignment. Notches, darts, and other markings are typically placed relative to seamlines to aid accurate matching during sewing.

Types and considerations. Seamlines can be straight or curved, with complex lines used in shaping garments such as princess seams or curved bodice panels. The amount of seam allowance—commonly around 1/4 to 5/8 inch (about 0.6 to 1.6 cm), depending on fabric, garment type, and finishing requirements—determines how the finished seam will sit. Finishing methods (household zigzag, serging, French seams, flat-felled seams) affect seam appearance and durability.

Construction process. After cutting pieces along seamlines, fabric pieces are aligned and pinned, notches are matched, and the seam is sewn. Pressing and finishing steps influence seam flatness, bulk, and durability. Proper seamline management is essential for fit, accuracy, and the overall appearance of the final garment.

In other contexts, the term seamline can also refer to the border where individual images or tiles are joined in mosaics or digital patterns, where its management affects visual continuity.