From McCall’s Complete Book of Dressmaking, Marian Corey 1951
You will always need a little extra fabric when using Checks, Plaids or Patterns. This will sometimes be noted in the Dress Pattern however, it is advisable, when using large Pattern Prints, to allow an extra drop. A drop is a repeat of the pattern- find a distinctive piece of the pattern & measure from this to the next place it can be seen. A pattern repeat can be anything from 5cm or however; it is unusual to find a drop longer than 45cm.
Checks & Plaids must match at the seams. They must also match at the waistline at Centre Front & Centre Back, & where the Sleeve is set in.
Patterns can match where it is best suited however; the above guidelines when followed create a balanced garment whether sewing Prints, Checks or Plaids.
All this matching has to be planned before cutting out the pieces of the garment. This trick with Tracing Paper simplifies it very much.
Try to start with the Front, pin the Paper Pattern to the material as directed (i.e. following Grain Lines etc) taking in to account the placement of the Print, Plaid or Check in relation to how the garment will be worn.
Take a piece of Tracing Paper & place over the seam edge. Try to include a Notch in the seam. Trace the pattern of the Print etc on to the Tracing Paper, the placement of the notch & the seam.
Pin this piece of Tracing Paper to the Paper Pattern piece which corresponds to the first, line the Print up according to the tracing & Pin the Paper Pattern down.
Proceed in the same way for all other corresponding notches and Paper Pattern pieces in the garment.