An waste knot - like its cousin, an away knot - is a temporary knot used to start an embroidery thread. The thread is secured by stitching over a tail of thread, and the knot is clipped from the fabric after the stitching has been completed.
The knot is made in four steps.
Insert your needle into the top of the fabric a short distance from where you will begin your embroidery, leaving a tail of thread oon the back side of the fabric.
Bring the needle up through the fabric from back-to-front at the location where your embroidery stitching will begin.