A hook hone or sharpener is a great part of anyone's fly fishing arsenal. Hooks need to be extra sharp, and one good test is to slowly slide a hook point across your thumbnail. If it does not stop, or hang up, then the hook needs sharpening. Sharp hooks account for a lot of lost fish. This two sided stainless steel file has a diamond grit surface on each side as well as a hook groove on each side. I like to use one side for large hooks, the other for small ones. Works on all bass and trout hooks you'd ever use.