I’m Sheldon, a son of logger. At first, I want just to free my dad from the troublesome sharpening. You know, due to the slow and physically demanding nature of hand files, it’s tiresome to sharpen the chain after a tiring day. He got my first design and gave me some suggestions for improvement. He was satisfied that this tool given him more time to enjoy his coffee. He said maybe I could start a business to help more workers.