Planeshift Clamps Upgrade For Work Sharp Professional Precision AdjustHapstone PlaneShift Series includes components of Hapstone RS adopted for other sharpening systems. Single clamp knife sharpeners have consistently been less adaptable than multi clamp systems when sharpening various blades, for instance, fillet knives. The Planeshift Clamps Upgrade is a dual clamp solution for Work Sharp Professional Precision Adjust knife sharpeners.