Choose Sewing Line or Cutting Line

What you are trying to accomplish

Tell PatternForge what the traced outline means: the line where you will sew, or the outer line where you will cut. This decision tells the app where seam allowance belongs.

Why it matters

The sewing line controls the finished shape and where joined pieces meet. The cutting line is the outer edge of a pattern that already includes allowance.

If you call a cutting line a sewing line, you can add allowance a second time and make the piece too large. If you call a sewing line a cutting line, the fabric may be cut without the allowance needed for construction.

Seam allowance is not wearing ease. It is material outside the sewing line that is consumed during sewing.

Step by step

1. Read the source pattern and its instructions before choosing. Look for “seam allowance included,” “seamline,” “stitching line,” or a stated allowance.
2. If two boundaries are printed, the outer boundary is normally the cutting line and the inner boundary is the sewing line. Confirm this against the pattern instructions.
3. Open the piece’s Get it ready or Shape area and find Which line did you trace?
4. Choose Cutting line when you traced the outer edge that already contains allowance. Read the confirmation, then choose Yes — cut on this line only when that is truly what the paper shows.
5. Choose Sewing line when you traced where the stitching belongs. PatternForge can then add the cutting line outside it with Seam Allowance.
6. If you are uncertain, choose I'm not sure — leave this unfinished and return to the source. What is common in other patterns is not proof—use the instructions for this pattern.
7. When adding seam allowance, choose an amount and corner treatment suitable for the actual construction. PatternForge does not prescribe one universal allowance for every fabric, seam, curve, or hem.
8. View both lines together. Make sure you can explain which one controls sewing and which one controls cutting.

What success looks like

• Cutting line is selected only when allowance was already inside the traced boundary.
• Sewing line is selected when the traced line controls stitching, with a deliberate cutting line added outside where needed.
• The displayed inside/outside relationship matches the paper source.
• Fold edges and other no-allowance edges are handled intentionally rather than receiving allowance by accident.

Common problems and recovery

• The piece becomes unexpectedly larger after adding allowance: Recheck whether the traced source was already a cutting line. Remove the duplicate allowance if necessary.
• The cutting line sits inside the traced line: The outline type or allowance direction is probably wrong. Return to Which line did you trace?
• The source says nothing about allowance: Do not guess from appearance alone. Check its instruction sheet, publisher notes, or a known physical measurement.
• Different construction edges need different treatment: Decide them from the sewing method. A single convenient amount is not automatically correct for seams, facings, hems, and fold edges.
• The allowance develops spikes or gaps: Repair the underlying shape first, especially short segments, tight inside curves, and self-crossing areas. Then inspect the cutting line again.
• You changed the outline after adding allowance: Recheck the derived cutting or sewing line around the edited area.

Quick safety check

Say this sentence aloud for the selected piece:

“I traced the ___ line. I will sew on the ___ line and cut on the ___ line.”

If you cannot fill all three blanks confidently, do not mark the piece ready yet.

Related tools and next step

Use Adjust Shape and Use Shape Check to inspect the boundary and allowance. Then complete the remaining evidence in Complete Pattern Check.