technique of mounting bristles and needles to waxed ends where the needle is pierced through the thread someway back, to prevent the bristle or needle from detaching during sewing
In twisted thread, piercing back can help prevent the mounting of the bristle or needle from unwinding.
In braided thread, piercing back even a single time usually holds very securely, since the plies of the thread cannot unwind. However, piercing back in braided thread can produce a bulge of thread behind the needle, especially if the point where the thread loops through itself cinches up to the back of the eye of the needle.