Buying a whetstone and learning how to sharpen a knife is a very valuable lesson in life.
I had two incredibly razor sharp knives that I used when I worked in the newspaper business for cutting off the ends of a damaged newsprint roll, called a "cutout" and for cutting off the cardboard heads and wrappers that came around the newsprint roll.
I would sharpen them on a whetstone with motor oil as the lubricant and they would be so sharp I could slice a piece of paper like a razor.
