lasting technique of driving a tack through the heel upper into the last at the back height or counter point to help keep the upper from sliding down the last while heel lasting
Makers avoid leaving a visible hole through the upper by tacking through an existing stitch hole of the backseam or heel counter cover. However, back height tacking leaves a visible hole in the lining.
A tack driven down at an angle prevents the upper from riding up the tack and falling down.