Tools: grindstone and knife.

1. The grindstone should be kept moist, and it is best to wash it with running water when sharpening.

2. When grinding the left blade, hold the blade tightly with both hands and fingers.

3. Fix this angle and move back and forth against the millstone.

4. When grinding the right edge, the angle is slightly larger than the left edge. It still keeps the same angle and moves back and forth against the millstone.

5. After grinding again, observe whether the blade is sharp. You can feel the touch by gently scraping your thumb along the vertical direction of the blade.