A sewing pattern piece is a map of one part of a garment. The solid outer line is where you cut, the dashed line inside it is where you sew, the long double-headed arrow is the grainline that must run parallel to the selvedge, and the small marks on the edges (notches) and inside the piece (dots, darts) show you how everything joins. Read the label first, then the lines, then the marks, and nothing on the page will surprise you.
This guide follows the symbols Sewly draws on its patterns, on screen and in the printed PDF. They match the conventions of most paper and PDF patterns; if a commercial pattern uses a symbol differently, its instruction sheet has a key, so check it once before you cut.
What are the symbols on a sewing pattern?
| Symbol | What it looks like | What you do |
|---|---|---|
| Cutting line | Solid outer line | Cut along it |
| Sewing line | Dashed line inside the cutting line | Stitch along it |
| Grainline | Straight line with an arrowhead at each end | Place it parallel to the selvedge |
| Place on fold | Bracket with arrows pointing at an edge, labeled PLACE ON FOLD | Lay that edge on the folded edge of the fabric |
| Notch | Short line from the cutting line into the piece | Match it to the notch on the next piece |
| Double notch | Two short lines side by side | Marks the back of the garment |
| Dot | Small filled circle | Transfer it: dart tips, pivot points, matching points |
| Dart | Two dashed legs meeting at a dot | Fold and stitch from the edge to the dot |
| Buttonhole | Line with a short bar across each end | Sew a buttonhole of that length |
| Button | Small open circle | Sew a button there |
Cutting line and sewing line
The solid outer line is the cutting line. Everything between it and the dashed sewing line is the seam allowance, the margin that ends up inside the finished seam. On Sewly patterns the allowance is already included: 1.5 cm (5/8 in) on woven fabrics and 1 cm (3/8 in) on knits by default, with a deeper allowance at hems and elastic casings. Because both lines are drawn, you always see exactly where the stitching goes, which helps a lot on curves and corners.
Many multi-size commercial patterns print only the cutting lines, nested one inside the other, and state the allowance in the instructions. In that case the sewing line is imaginary: you keep the fabric edge on the matching line of your machine's throat plate. Before you cut any pattern, check two things: whether the allowance is included, and how wide it is.
Note: Hem edges usually carry a wider allowance than seams, for example 2.5 cm (1 in) on wovens and 2 cm (3/4 in) on knits by default on Sewly patterns. The dashed line along the hem shows the finished length.
The grainline arrow
The straight line with an arrowhead at each end is the grainline. It tells you how the piece sits on the fabric: the line must run parallel to the selvedge, the woven edge of the fabric that does not fray. It does not matter which way the arrows point; what matters is that both ends sit the same distance from the selvedge.
To place it, measure from one end of the arrow to the selvedge, then from the other end, and shift the piece until both measurements match. A piece cut even slightly off grain can twist around the body after the first wash, so this one check is worth the extra minute. On knits the arrow runs along the ribs (the fine vertical columns of loops), which puts the greatest stretch around the body.
Some pieces carry a note as well as an arrow: "Cut on the bias (45°)" for binding strips, or "Stretch runs along the length" for knit neckbands and cuffs.
Place on fold
A bracket with arrows pointing at one edge, labeled PLACE ON FOLD, means that edge goes exactly on the folded edge of the fabric. You cut through both layers and, when you open the fabric, you get one symmetrical piece twice as wide as the paper. A fold edge has no seam allowance, so do not add one, and do not leave a gap between the paper and the fold: 5 mm (1/4 in) of gap becomes 1 cm (3/8 in) of extra width.
Do not confuse it with a fold line, a long dash-and-dot line inside a piece. A fold line shows where the fabric folds back on itself after cutting, as on a buttoned front with a cut-on facing or the vent of a pencil skirt.
Notches: single and double
Notches are short lines that start at the cutting line and point into the piece. They line up two edges that are sewn together: front side seam notch to back side seam notch, sleeve notch to armhole notch. They also mark where something starts or stops, such as a pocket opening or the bottom of a zip.
By convention a single notch marks the front and a double notch marks the back. On a sleeve, the single notch goes to the front armhole, the double notch to the back armhole, and a notch at the top of the cap meets the shoulder seam. On Sewly sleeves the front notch sits 7.5 cm (3 in) and the back double notch 8.5 cm (3 3/8 in) up from the underarm, so you can tell left from right even once the paper is gone. Some patterns add triple notches for a third kind of seam; the principle is the same.
Dots, darts and inside lines
A dot is a matching point: the tip of a dart, the corner where you pivot, the end of a gathered section or the top of a pleat. Transfer every dot before you unpin the paper.
A dart appears as two dashed legs that start at the edge and meet at a dot, the tip. On Sewly skirt darts and bust darts, a notch on the cutting line also marks where each leg meets the edge. A double-pointed dart, used at the waist of fitted dresses and tops, is drawn as a narrow diamond with a dot at each end.
Inside lines with other dash patterns have their own jobs: a long-and-short dashed line marks the center front, a dotted line marks where to gather or where an elastic goes, and a line down the middle of a trouser leg marks the grain and the crease.
Reading the label
Every piece has a label near its middle. Read it before anything else:
- The name: Front, Back, Sleeve, Pocket bag, Hood.
- How many to cut: "Cut 1 on fold" (one symmetrical piece), "Cut 2 (a pair)" (a left and a right, which you get by cutting through two layers of fabric), "Cut 4 (pairs)" (two lefts and two rights, such as in-seam pocket bags).
- A note: "Interface half", "Cut on the bias (45°)", "Stretch runs along the length".
Large plain rectangles (waistbands, ties, gathered skirt panels) are often not printed at all. Sewly lists them with their cutting dimensions so you draw them straight onto the fabric with a ruler and chalk, which saves paper and tape.
How to read a new pattern, step by step
- Print the pattern and measure the test square before anything else (5 cm and 2 in on Sewly patterns). If it is off, nothing else will fit.
- Check the pieces list against the pieces you have, and note the cut counts.
- Read each label and write the size or the name of the measurement profile on the paper if you will reuse it.
- Find the grainline and any place-on-fold edge on every piece.
- Highlight the notches and dots so you do not miss them when cutting.
- Look at the cutting layout for your fabric width and plan which pieces go on the fold.
- After cutting, transfer the markings before you remove the paper.
Common mistakes and how to fix them
- Cutting on the sewing line. Each seam ends up 3 cm (1 1/4 in) smaller, 1.5 cm on each piece. If you have not sewn yet, recut; if you have, sew 3 mm (1/8 in) seams and accept a closer fit, or use the pieces for a smaller garment.
- Ignoring double notches. Sleeves go in backwards and twist forward. Unpick, swap the sleeves left for right, and match double to double.
- Grainline eyeballed. The garment hangs crooked. There is no real fix after cutting except recutting the piece, so measure both ends.
- Seam allowance added twice. If a pattern already includes the allowance and you add more, everything grows by 3 cm (1 1/4 in) per seam. Read the pattern's statement before you cut.
- Gap at the fold. The piece is wider than drafted. Push the paper right against the fold and pin that edge first.
- Marks lost with the paper. Dart tips and dots disappear when you unpin. Lay the paper back on the piece, align the cutting lines, and mark again.
Once the symbols make sense, the next step is placing the pieces on the fabric: see laying out and cutting fabric on grain.