The wind is the natural winnower, but man can help the wind by exposing the mixed chaff and grain. This he throws up on the winnowing fan against the wind, the wind blows away the chaff and the heavier grain falls to the ground. The best instrument with which to do this is naturally an oar-like pole, broadened at the end to serve as a shovel. Such an instrument was the πτύον (ptúon) or winnowing fan.