Tailor's tacks are loops of thread used to transfer pattern markings and other important details onto fabric. They are particularly useful for thick fabric, or fabrics that are difficult to mark, such as wool.
This video demonstrates how to use tailor's tacks to precisely mark button placement on two layers of fabric, but they can also be used to mark darts, pleats, or any other placement notches. This is a lovely couture technique for you to add to your sewing repertoire!
Here is a short video that demonstrates how to sew tailor's tacks: