The whetstone is a piece of natural abrasive stone, shaped like a prism, cylinder or cone, usually from sedimentary rocks rich in silica, which the mowers carried with them in special containers (whetstone holders) attached to their belts.
The whetstone was used to sharpen the blade of the scythe which, during cutting operations, could lose its edge due to wear or contact with hard materials (stones, pieces of wood) present on the ground.
The mower placed the scythe in a vertical position, with the blade facing upwards, and rubbed the whetstone alternately on the front and back of the blade.