- 1). Turn the jacket inside out, and lay on a flat, even surface. Take a seam ripper, and undo the seams to be altered on the jacket. For example, if you are going to alter the sleeve length or the overall length of the jacket, undo the bottom hem seams. These seams will not affect the gussets. When adjusting side seams, only undo the stitching that holds the main pieces of the jacket together, leaving the gussets intact.
- 2). Pin the new seam in place. For the bottom hems of a jacket, you can simply shorten or lengthen the jacket, and the gusset will retain its shape, gaining or losing a small amount of volume. When hemming near the gusset underneath the arm, pin the new seam in place, allowing a small portion of the gusset to be tucked into the newly defined seam.
- 3). Sew along the newly pinned seams using a sewing machine. Turn the jacket right side out, and ensure that all newly created seams fit correctly. If the jacket fits correctly, turn the jacket inside out again, and trim any excess fabric.
- 4). Turn the jacket right side out, and iron the new seams in place to create crisp, clean lines, and to get rid of old seam creases.
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