Many guided knife sharpeners include L-shaped Allen keys, the least expensive tool to handle hex screws. Hex screwdrivers are much easier to use than Allen keys. If you use your sharpener on a regular basis, hex screwdrivers will make your life comfortable. 1.5 mm TSProf K03 - small components Blitz 360 - many components 2 mm Hapstone Angle Gauge Holder Hapstone K1 - guide rod coupling TSProf K03 - body Blitz - most components Blitz 360 - many components 2.5 mm Hapstone R1 - stone holder Hapstone V7 - stone holder TSProf K03 - body 3.0 mm Hapstone R2 Lite - clamps TSProf K03 - body TSProf K03 - clamps 4 mm Hapstone Modular Platform Hapstone R2 - full-sized clamps Hapstone R1 - most components Hapstone M2 - three-point guide, stone holder Hapstone V7 - three-point guide Hapstone K1 - most components TSProf K03 - whole-milled clamps