in patterning some lined Derbies, a pair of reference points near the bases of the tongue tab, behind the stay stitches, marked on or punched through the vamp, vamp lining, and quarter linings, that show the leading edge of where each Derby nose will pass through the vamp lining and vamp to come up under each quarter tab
The points are used to fit up those pieces to ensure proper alignment.
covered extensively in Uppermaking for Bespoke and Orthopaedic Shoemakers