Definition
Clipping and notching means cutting into the seam allowance of a curved seam, with straight snips or small V-shaped wedges, so it lies flat once turned and pressed.
When a curved seam is turned right side out, its seam allowance no longer fits the space it must lie in. On an inward curve the allowance edge is too short and pulls; on an outward curve it is too long and bunches. Cutting into it fixes both.
- Clip concave curves, which curve inward like a neckline or the center panel of a princess seam: make straight snips perpendicular to the seam so the allowance can spread open when turned.
- Notch convex curves, which curve outward like a rounded collar, a patch pocket corner or the side panel of a princess seam: cut small V-shaped wedges out so the allowance can fold in without overlapping.
- Corners: cut across the point diagonally, a few millimeters from the stitching, and taper the sides on sharp angles.
Cut to within 2 to 3 mm (about 1/8 in) of the stitching, never through it. Space the cuts 1 to 2.5 cm (3/8 to 1 in) apart, closer on tight curves. Trimming the allowance narrower first, as in grading seams, means fewer cuts are needed.
This is not the same as the notches printed on a pattern, which are matching marks. On outward curves, trimming the allowance with pinking shears (see pinking) can replace notching.