Before cutting the various pattern pieces, decide if both the right and left pieces will be cut at the same time, or individually. When working with an even plaid with bold definition, folding the fabric and cutting both sides at once is easy. Pin through the fabric matching the top side to the underside so that when you cut, both pieces are identical.
When the plaid is uneven or vague in lines, consider cutting one piece at a time. Remember to flip the pattern pieces over so that you cut a right side and a left side. Marking the side of the pattern piece you have already cut before removing it from the fabric can help.
The style of the pattern dictates the order of the layout of the pattern pieces. If the back is cut on the fold, it is placed first because you have no choice of the location of the shoulder seams in the plaid. Pay attention to where the hemline falls on the plaid. Position the piece so that it does not fall on an obvious horizontal line. This allows you to adjust the hem without bringing attention to this area. Once the back is in place, trace the lines of the plaid at the notches of the shoulder and side seams on the seamline.
Lay the front pattern piece over the back pattern, matching the notches. Transfer the markings on the back to the front pattern.
Now, place the front pattern piece on the fabric intersecting the plaid at the shoulder and side seams in the same location. If the back pattern piece has a center back seam, place the front pattern piece first. Position the piece so that when center-front meets center-front in the finished jacket, a plaid is completed.
This is desirable in a bold plaid so we select a pattern with a shaped center back seam in this case. Trace the intersections of the plaid at the notches on the shoulder and side seams on the seamline. Transfer these markings to the back pattern. Then place the back piece, matching these intersections.
Lay the front facing on the front pattern, and trace the plaids. Pin the front facing on the fabric, matching the lines. The sleeve pattern for many jackets is in two pieces. There are two markings, a circle and a notch, between the sleeve cap circle and the underarm square. One or both of these will be on the upper sleeve. Use the higher marking for matching. Most of the time, it is the circle and the lower one is a notch. But, sometimes this is reversed. Just remember to use the higher one on the front side of the upper sleeve for matching.
There is a section of the seam line on the under sleeve indicated by two circles that is longer than the upper sleeve. This replaces the elbow dart. The pattern will instruct you to either ease this onto the upper sleeve or stretch the upper sleeve to fit. Measure the difference in distance between the circles on the upper and under sleeves. Tuck this out of the under sleeve so that the plaids will match (Figure 2).
After making the tucks, the grainline may curve. Re-draw the grainline connecting the two ends with a straight line. The upper sleeve is matched before the under sleeve. Here is where things get a little tricky. The sleeve cap is larger than the armhole. Ease must be included in the placement of the sleeve. Mark 1/2" away from the circle marking the apex of the sleeve cap. The sleeve is not eased in this area. Measure the distance from this mark to the upper circle on the seam line. Measure 1/2" from the shoulder seam in the armhole on the jacket front. Measure the distance from that point to the upper circle on the seam line.
In a sample project, the sleeve cap measured 4/8" and the armhole measured 3 5/8"; a difference of 1/2". So, for every inch of armhole, I eased just barely over 1 1/8" of sleeve. For this example, the plaid intersects the seam line 1" above the upper circle of the armhole. So, the sleeve would be placed so that the plaid intersects 1 1/8" from the upper circle.
After pinning the upper sleeve in place, match the side front seams of the upper sleeve to the under sleeve in the same fashion as the other pieces. Trace the intersection of the plaid on the upper sleeve. Lay the under sleeve in place over the upper sleeve and trace the markings (Figure 3). Then pin the under sleeve to the fabric, matching the plaid.
The collars are next. The under collar is cut on the bias. Both sides of the upper collar should intersect the plaid in the same place. If the back of the jacket is cut on the fold, match the center back of the upper collar to the fold line which will be a central point of the plaid. Here, consider both vertical and horizontal locations of the plaid. For instance, if a bold horizontal line of the plaid ended just below the neck edge, place the collar so that a second bold line would not appear at the bottom of the collar. If the bold line is far away from the neck edge, then position the collar so that once it is completed and applied, the bold lines would be equi-distance all the way up to the back, including the collar. If the jacket has a center back seam with a completed plaid at the back neck, match that. If the plaid is not completed at this point, you are not limited to the same central point of the plaid that was used for the center front.
Align the center back of the collar with the central point so that both sides will be identical. Cut all the pinned pieces leaving ample fabric for the pockets, flaps, and/or welts. Mark the location of the pockets on the front pieces. Lay the pocket pattern in the position it will be when completed. Trace the location of the plaid on the pattern. If there is a front dart intersecting the location of the pocket, match from the edge closest to the center front over to the dart.
Your plaids will match, and you'll love your new jacket!