Vicki wanted some more information on prick stitching, so I decided to do a whole post on it.
The prick stitch is a variation of the back stitch. It is mainly used as the hand stitched version of machine understitching, to keep facings/linings from rolling to the outside of the garment. The prick stitch is also one way to install a zipper by hand, known as "hand picking a zipper". Recently, I've used the prick stitch on both the Diamond's gown bodice top edge and skirt slit opening and on the silk dress' bodice top edge. In the past, I hand picked the zipper for the American Beauty gown and also for the brown 50's Easter dress.
There are some advantages to working the stitch by hand. The major advantage is being able to put the stitches in places where you can't by machine, such as tight corners or curves or wherever the sewing machine foot can't go. The disadvantage is that, of course it takes a bit more time to complete when doing hand stitching. Do keep in mind that any time invested in hand stitching, regardless of stitch, will result in a better and more couture-style finish.
Here's how to do it:
1. Once the facing/lining has been attached, with the lining side facing you, secure the thread at the right hand edge of the fabric. This stitch is worked from right to left. Bring up the thread and needle at point A, 1/8" to 1/4" away from the top edge of the fabric.
2. Place the needle back into the fabric at point B, 1/8" to 1/4" away. The needle must go through the lining and all the seam allowances, but not through the fashion fabric on the outside.
3. Bring the needle out again at point C, about 1/4" away (see photo above, too).
4. Repeat steps 1 through 3 across the fabric. Point C from step 3 will become point A in step when repeating the sequence.
Note the fashion fabric front below, no stitches are showing.
On the inside, you can see the longer stitches through all the seam allowances (well, except for the second one, oops!)
When hand picking a zipper, the steps are the same, except that you'll be stitching through the fashion fabric and the zipper tape, as shown below in the red thread (black has been used for the hand basting):
Note the back of the zipper tape, where you can see the longer stitches taken behind the fabric and zipper tape:
Regarding stitch length, the stitch lengths above are only guidelines - you might want a larger stitch to hand pick a zipper, as well as a larger stitch if your fabric is bulky
Lastly, this stitch takes practice to get it even and consistently spaced, not only from one stitch to another, but evenly spaced from the top edge. It helps to mark a line with a water soluble marker when first starting so that you stay consistent. It is especially important to have a consistent line of stitching when hand picking a zipper - that stitching will be on the outside for the whole world to see! For the American Beauty zipper, I marked exactly where every stitch would be.
Parting Shot: Studio helpers! Whenever I have some sorting or a task that involves picking out all the "x" colored items from a group of items, my daughter is usually happy to help. In this case, what little girl wouldn't be happy picking through a bag of lace and ribbons looking for additions to a new project?