WHAT IS IT?
A French tack is a thread chain that connects layers of fabric together loosely, usually at the hemline of a garment. The tack is made of regular sewing thread that’s hand crocheted to form the chain and attached between the garment and its lining.
French tack under hem of dress
WHEN DO YOU USE IT?
Use a French tack to keep the lining from separating from your garment. It’s used when the lining and the garment are hemmed separately, so the layers are completely free from each other. If you skip the French tack, you’ll be able to separate the layers and iron each one individually, so that’s one reason not to sew the tacks. In the end it’s up to you. You can always add them later if you find the lining moves too much. French tacks are sewn at the very end, once the garment and lining are both sewn and hemmed.
For a lined garment, two French tacks placed at the side seams are all you need.
HOW TO SEW A FRENCH TACK
Thread a handsewing needle with doubled thread. Start the tack by taking a few stitches in the garment to secure the end, about ¾” (1.9cm) above the fold of the hem. Take another stitch, but don’t pull the thread all the way through. Leave a loop of thread big enough for your fingers to fit through, about 3″ (7.6cm).
Hold the loop open with the forefinger and thumb of one hand; if you are right-handed, use your left hand. With your other hand, grab the thread through the original loop, pulling the original loop tight. This is the beginning of your hand-crocheted chain!
Continue pulling a new loop through each loop you make.
Stop once the thread chain is ¼”–¾” (1.3cm–1.9cm) long. You don’t want to make too long of a tack or the layers will separate. Too short of a tack won’t allow the lining to move freely.
When the tack is the right length, pass the needle through the open loop and pull it tight to form a knot.
Make sure the lining is smooth from the top of the garment. Usually the lining is hemmed shorter than the main fabric, so make sure you’re aligning the lining to the garment correctly. Sew a few stitches through the lining to secure the tack. Knot the end and trim the thread tails.
Source : The Sewtionary An A to Z Guide to 101 Sewing Techniques + Definitions
About the Author : Tasia ST. Germaine