Matching plaid isn’t difficult, but is time consuming.
Each piece needs to be cut separately.
First, determine how often the pattern repeats. Some plaid, like the purple plaid, actually had two different horizontal and vertical prints, so the pattern repeat was nearly 12″ both along the width and length. The pink plaid, pictured below repeated every 4″.
For multiple cuts of the same piece, cut the first piece, leave the pattern piece pinned to the fabric flip and match up the pattern before cutting the next. For fabrics with an obvious right and wrong side this is important to flip to ensure pieces are cut for both right and left sides.
Pattern notches are the best way to line up the plaid so they’ll match when sewn together. Find a particular line in the pattern to line up with the pattern notches. It is important that this line not be on a curved or eased seam.
To match the pattern for the sleeves, match the print at the bottom of the arm and the start of the sleeve. Also, match the pattern notches on either side of the sleeve to ensure the plaid will line up at the sleeve seam line, but also across the jacket.
When pinning the pieces together for sewing, check to make sure the lines are lining up as you go. Sometimes the material can stretch or slip when pinning or sewing.
It is difficult to match the plaid on curved or eased seams, the more curved or eased the less it will match.