Centered and lapped applications. The centered application is best for a heavy fabric; on a garment it’s usually used at a center back seam. Machine baste the placket opening; clip the bobbin thread at 1-inch intervals; press the seam open. With the top of the opening facing you, extend the right seam allowance.
Open the zipper and position it facedown on the seam allowance with the top stop 1/4 inch below the top seam (1/2 inch if your garment has a facing). Using a zipper foot, machine baste the zipper tape along the stitching guideline.
Close the zipper: sew the left tape to the left seam allowance. On the right side of the garment, baste through all layers 1/4 inch from the center. Stitch just outside the basting in two steps, starting each time at the bottom center of the placket. Remove all basting.
Lapped application This is suitable for light to medium-weight fabrics: in a garment, it’s most often used at the side seam. Prepare the zipper seam and machine baste the zipper to the tight seam allowance, as for a centered application. Turn the zipper faceup; stitch along the fold that lies between the teeth and the seam. On the right side, spread the fabric flat over the unstitched part of the zipper: baste 3/4 to 1/22 inch from the seam. Stitch close to the basting.