Threads Logo Threads Logo Facebook Email Pinterest Twitter Instagram YouTube Icon Headphones Icon Favorite Navigation Search Icon Forum Search Icon Main Search Icon Close Icon Video Play Icon Indicator Arrow Icon Close Icon Hamburger/Search Icon Plus Icon

10 Patternwork Skills

Key refinements for accurate sewing

Threads #200, Dec. 2018/Jan. 2019
Article Image

When I fit a garment, I work with a muslin on the body. Then I transfer the changes from the muslin to the original paper pattern. Some sewers like to dismantle a fitting muslin and use the fabric pieces as a pattern. I don’t because the muslin can become distorted during the fitting, sewing, and disassembly process.

A paper pattern is stable and, therefore, delivers the precision I demand of a pattern, especially one I’ll want to use more than once. First, I walk and true all the seamlines on the original pattern, to ensure they are accurate. After I’ve finished a fitting and made my adjustments to the paper pattern, I refine it to correct any issue that occurred through transferring fit changes from muslin to paper.

This work requires nothing more than a pencil, a straight ruler, and a curved ruler. It’s worth the time. Your pattern will be more accurate and easier to sew. You’ll also gain confidence in handling commercial and self-drafted designs and will be able to make changes for fit or style.

Think seamlines

When doing your initial patternwork, ignore the seam allowance and cutting line. For beginners, I suggest cutting off the seam allowances. I do this, too, when I’m tackling an intricate or confusing patternmaking issue. Modify and correct all the seamlines, then add the seam allowances.

Draw the seamlines on the patterns if they’re not provided. Use a ruler to ensure the seamlines are accurate and precise. Imprecision in your patternwork means you have more to question when sewing the garment. I keep my patterns true to 1/16 inch; many sewers find accuracy to 1/8 inch works well. A see-through ruler with a 1/8-inch grid also has edge markings at 1/16-inch intervals, so it’s easy to work precisely.

Stay true

The process of reviewing and correcting a pattern’s seamlines and other elements is called truing. You’ll “walk” the seamlines to determine if they are of equal length (minus deliberate ease, darts, gathers, or pleats). If you find a discrepancy, you can decide how to correct it. If you’re concerned about the changes you’ve made, make another muslin to check the fit.

You can walk and true patterns without seam allowances. However, if you leave the allowances on and true them along with the seamlines, as I demonstrate, you’ll ensure they align properly. This enables you to construct the garment accurately.

10 techniques

These 10 techniques are the backbone of more complex patternwork. Practice these methods on each pattern you alter, and you’ll soon be ready to embark on making more adventurous design changes.


1. Walk a straight seam

Lay one pattern on top of the other as if to sew the seam. Match the seamlines at one end. At the opposite end, the seamlines should be the same length.

If they are not, you have three choices: Subtract from the longer line; add to the shorter line; or split the difference, as shown. In the last case, add half the difference to the shorter seamline and subtract half from the longer one. Splitting the difference is usually the safest option. If you have other reasons, based on fit or design, for preferring to shorten or lengthen the final seamline, it’s fine to do so.


walk a curved seam

2. Walk a curved seam

Lay one pattern on top of the other, with the seamlines aligned at one end. The lines will diverge along the curve: At this point, pin straight down into the pattern to anchor the two sheets. Pivot the top pattern so that the two seamlines match for some distance. When they diverge, pin and repeat.

Continue pinning and pivoting until you get to the opposite end of the seam. Both seamlines should match exactly at the end of the seam. If they do not, choose how you will deal with the difference (see “1. Walk a straight seam”).

The cutting lines also align and diverge and often are not the same length, especially when opposite curves are joined. Ignore them and focus on the seamline.


3. Remove ease in a curved seam

Many side-front princess seamlines are intentionally drafted longer than the adjoining front princess seamline. Walk the seamlines (see “2. Walk a curved seam”). If the side-front princess seamline is slightly longer than the front, then this difference is probably intentional ease (A).

My fitting and sewing preference is for these seamlines to be the same length. I usually remove intentional ease, or keep 1/8 inch to 1/4 inch. Alter the pattern at the armhole or the shoulder seam intersection (B).


4. Establish notches

Notches help you sew the garment together with precision. Check their placement as you walk each seamline. Correct or add notches as needed.

As you walk a seam, it’s easy to see if the notches do not line up precisely, and to reposition or add a notch for accuracy. To do so, lift the upper pattern’s edge, draw a notch on the bottom pattern (A), replace the upper pattern piece, and trace the notch from the bottom pattern (B).


5. Position ease in a curved seam

Intentional ease along a princess seam should be distributed across the area of the bust apex. Walk the seamlines, starting at the patterns’ lower end. Several inches below the apex, establish notches on both pattern layers. Repeat, walking the patterns downward from the seamlines’ upper end. Add a notch above the apex level on both layers. Between the notches, the side princess seamline is longer than the front seamline. By precisely matching the notches when you sew the seam, the ease will be distributed across the apex. If desired, you can also move existing notches to spread the ease over a longer portion of the seam, as shown.


6. True dart legs

To create the proper shaping along a seam that intersects a dart’s legs, you need to fold the dart as it will be sewn, and true the pattern edge. The first fold is on the “leading” dart leg, the one toward which the dart will be pressed. Fold the pattern on that leg, with right sides together. Working over the corner of a table, bring this fold to the second dart leg, and crease the paper (A). Pin in place. Reblend the intersecting seam if necessary (B), and cut along this new cutting line.

Unpin and unfold the pattern; there is often a triangle-shaped extension from the dart at the seamline (C). Having a precise dart extension will help you line up the dart legs when pinning and sewing the dart.


7. True seams with darts

When walking a seam that intersects a dart, skip over the dart intake. Start walking the seam with the darted pattern piece on the bottom. When you reach the first dart leg, place a small mark on the top pattern’s seamline (A). Move the top pattern up and place this mark on the second dart leg at the seamline (B). Continue walking to the end of the seam in the usual way. Handle seams with pleats in the same way.


8. True the legs of large darts

Darts with large intakes, such as French darts (straight or curved) or a dart for a full-busted woman, can be unwieldy to sew when the dart intake remains in the pattern. To facilitate sewing these darts, draw a narrow 1/4 inch or 3/8 inch seam allowance along each dart leg, within the dart intake. Work with a ruler to ensure accuracy. Add notches, if desired, on the dart legs

Cut away the remaining dart intake within the dart. When sewing, simply bring the two cut edges together, sew the dart employing the chosen dart seam allowance, tapering to nothing where the dart point intersects the fabric fold.



9. True tricky intersections

In my experience, some commercial patterns’ seams are not trued as precisely as I’d prefer. This occurs at tricky intersections such as two-piece sleeve seams and armscye princess seams, where the seam meets the garment edge at a steep angle. Even if the seamlines are the same length, the seam allowances are different shapes, and they make it confusing to align the fabric layers accurately for sewing. Here’s how to correct those seam allowance ends. Walk the seamlines. About 1 inch from the intersecting seam, pin the pattern pieces together precisely on the seamline. Observe how the seam allowances align at the seam end.

Excess allowance

If the top allowance extends beyond the lower allowance (A), fold open the pattern and blend the seamline and cutting line, using a curved ruler as a guide (B). Trim the excess along the new cutting line. Unpin the patterns; the top layer can align to the adjacent pattern (C).

Insufficient allowance

If the top allowance doesn’t extend all the way to the bottom layer’s edge, add to it (D). Tape a paper scrap where the seam allowance is too short. Extend the cutting line onto the scrap, then trim along it (E).

Fold open the top pattern again and redraw the cutting line across the scrap paper (F). Trim along this line. Unpin and unfold the amended pattern. Trim the remaining edge, if necessary, along the adjacent cutting line (G).


10. Establish horizontal balance lines

I use horizontal balance lines (HBLs) as visual guides for fitting. The HBLs should travel around the garment at the same level on each garment section. To establish them on the pattern, begin at the center front. Lay the pattern on a gridded board with the center-front or front fold on a gridline. Draw an HBL perpendicular to the vertical line across the pattern. On a skirt, place it at the fullest hip width; on a blouse or sheath dress, place it above the waistline and several inches below the bust-point level.

To mark corresponding HBLs on the remaining patterns, place an adjoining pattern atop the one just marked, and walk its seamline. When you come to the HBL, make a small mark on the seamline. Place this pattern on the gridded board with the grainline on a grid mark, and the mark on a crosswise gridline. Using a straightedge as a guide, draw the HBL at this level. Repeat for any additional pattern pieces.

Sarah Veblen teaches in person, online, and through videos. View her pants-fitting video series on

Photos: Mike Yamin. Illustrations: Rosann Berry.

Sign up for the Threads eletter

Get the latest including tips, techniques and special offers straight to your inbox.

Sign Up
View PDF

Threads Insider

Get instant access to hundreds of videos, tutorials, projects, and more.

Start Your Free Trial

Already an Insider? Log in

Subscribe to Threads today

Save up to 37% and get a free gift



  1. user-6068310 | | #1

    Great article! You recommend cutting off the seam allowances of the pattern in the beginning but how do you then sew a muslin without seam allowances? I was taught to transfer the seam allowance onto the muslin with a pencil, sew, then bring it back to the pattern to examine the differences and make your changes. Secondly, I've noticed with many commercial pattern, the ease that they provide is way more generous than a ready-to-wear outfit which makes homemade close look frumpy. Especially if you don't have a waistline or hips that match the patterns measurements. How do you recommend adding back "ease' once you've fitted the pattern? (wovens, not knits).

  2. User avater
    sunnylutz | | #2

    This is a wonderful article. I've never walked the seam lines of commercial patterns before but I KNOW I've sewn patterns where things just didn't line up. I've always assumed it was a mistake on my part but maybe not. Thanks for these tips! This is why I love Threads!

Log in or create an account to post a comment.

More From Threads

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |

Threads Insider Exclusives

View All
View All


  • Sign up for the Threads eletter

    Get the latest including tips, techniques and special offers straight to your inbox.

    Sign Up
  • Bernina Sponsored Content

    Where to Buy

    Locate a BERNINA store in your area.