Hem rolling on knits

Understitching that wanders away from the seamline, leaving the facing visible from outside, comes from sewing too fast or not keeping seam allowances pressed toward the facing. Slow down and hold allowances flat as you stitch.

Topstitching that wanders off an even line instead of running parallel to the edge usually comes from sewing too fast without a guide. Use the presser foot edge as a guide and slow down on curves.

A facing edge that rolls to the outside instead of staying tucked inside usually means it lacks understitching or the interfacing is too light. Understitch close to the seam and match interfacing weight to the fabric.

Topstitching that gathers fabric into small folds instead of lying flat comes from tension too tight, a stitch too dense, or sewing bulky layers without a walking foot. Loosen tension and use a walking foot.

Seam allowances unraveling into loose threads after the first wash mean the edges weren't finished before construction. Serge, zigzag, pink, or bind raw edges before or after sewing the seam.