Flat Diamond Shaped File designed to sharpen any Silky Saw without hardened tips on the teeth.
One way you can tell if the saw has hardened teeth, is to take a look at a brand new saw and have a look at the tip of the teeth. If the tip of the teeth is black, it means it has been hardened and can't be sharpened. E.g - Gomtaro, Zubat and Tsurugi can't be sharpened.
Saws you can sharpen because they don't have hardened teeth are: