|Pintucks are tiny folds sewn into the fabric to add texture and decoration. There are usually several placed together in vertical rows, like on the bodice of a top or dress.
If the pintucks run from one seam to another, there is no need to tie them off. But if the pintucks end in the middle of the fabric, it is necessary [normally] to pull the threads to the wrong side of the fabric, and hand tie them to secure.
This technique is for pintucks that end in the middle of the fabric. You will be sewing along a fold in the fabric, 1/8 inch [or a little more] from the fold, using a regular machine needle.
Get ready to 'think outside the box' when it comes to threading your machine. Each pintuck is sewn with a single thread from your bobbin. Remove the top spool of thread.
With the bobbin in your machine, pull thread from your bobbin. Pull enough out that it is about a foot longer than the length of your pintuck. Put this thread through the needle, threading it the opposite direction [a needle threader really helps do this]. Keeping using this thread to completely thread the machine...the machine will be threaded as usual, you're just starting at the needle and working backwards. Just lay the extra thread on top of your machine. The thread should go directly from the bobbin to your needle, no slack. You're ready to sew the first pintuck.
You start the pintuck where you want the finished end to be [in the middle of your folded bodice, not at the raw edge]. Sew along the edge of the fold, until the pintuck ends at the edge of the fabric. Cut thread and remove bodice from machine. Remove any leftover thread from the top of the machine. Voila, the pintuck is finished, and no thread tails to tie off.
To do the next pintuck, pull thread from bobbin again, and rethread machine as before.
In the link above, you'll see an image of how the pintuck stitching should look when you've completed one. The second image shows an example of how pintucks can begin in the middle of a project.