This symbol is on many of Hourglass Patterns' directions. Below are 3 images that will help you perfect your binding application on sleeveless garments. Many of my patterns have you apply the binding to the raw edge before you sew the side seam. This is a much quicker method and is perfect for many applications. I say many because there are times when this method will not work; and you will need to use the other method where you sew the shoulder and sides 1st, then apply a finished binding.
Pin, pin and pin to get it right. I always baste 1st before using my serger.
Align the binding tops and seams, then match the notches.
Sew from the hem to the binding and as you get to the binding increase your seam allowance; this makes it easier to tack down in the final step below.
Professional results with not fuss.
