An American classic, and only 10 dollars. You dip it in water if there's water around, and grind the ax sharp. The water just floats the dust away, so it can be more effective. No room here for ax sharpening lessons, but they're all over YouTube. This one's too good and cheap not to get. Three inches across, an inch thick, for easy carrying in a pocket. One side is coarse grit and the other is medium.