A pleat is a fold or series of folds in fabric that add fullness into a garment. There are lots of ways these folds can be arranged and stitched to form different types of pleats, two types are used in Sewing Basics for Every Body - knife pleats and inverted pleats.
All pleats are different combinations of the most basic kind of pleat—the knife pleat, which is formed with just two folds going in opposite directions to each other.
An inverted pleat is formed from two knife pleats lying in opposite directions and positioned side by side.
HOW TO SEW A KNIFE PLEAT
1 First, you need to accurately transfer the fold and placement lines of your pleat from your paper pattern onto the wrong side of your fabric (see Transferring Pattern Markings). All pleats are shown with these two lines and an arrow showing you in which direction the fold line should lay when looked at from the right side of the fabric.
2 Once you’ve marked the pleat on your fabric, bring the fold and placement lines together with the right side of the fabric touching, pin, and baste (tack) for approx. 2 in. (5 cm) along these lines to hold them together.
3 Press the tuck that has been formed in the fabric so that the original fold line is lying in the direction indicated by the arrow on the paper pattern—note that this arrow assumes that you’re looking at the right side of the fabric, if you’re looking at the wrong side it will lay in the opposite direction. For example, the tucks of the knife pleats in the front of the Harper pants should lay toward the side seam when looked at from the outside of the pants, but will look as though they’re laying toward the center front seam when looked at from the inside of the pants.
4 With the pleat pressed and pinned in place, baste across the top of the pleat to keep it in the right position while the rest of the garment is being assembled. Remove the basting once the garment is complete.
HOW TO SEW AN INVERTED PLEAT
1 Repeat step 1 as for How to Sew a Knife Pleat, opposite. Once you’ve marked the pleat on your fabric, bring the two outer fold lines together with the right side of the fabric touching, pin, and baste for approx. 2 in. (5 cm) along these lines to hold them together.
2 Flatten the tuck that has been created in the fabric so that it lies flat against the rest of the garment, with the basted together fold lines level with the placement line. (This pleat will look squashed in the middle, rather than pressed to one side like the knife pleat.) Press carefully in this position.
3 With the pleat pressed and pinned in place, baste a square around the top of the pleat to keep it in the right position while the rest of the garment is being assembled. Remove the basting once the garment is complete.
Find more techniques alongside step-by-step garments for all ages, genders and body shapes in Sewing Basics for Every Body by Wendy Ward.