'Threshing floors' in the Bible

And they told David, saying, Behold, the Philistines are fighting against Keilah, and are robbing the threshing-floors.

Then was the iron, the clay, the brass, the silver, and the gold, broken in pieces together, and became like the chaff of the summer threshing-floors; and the wind carried them away, so that no place was found for them: and the stone that smote the image became a great mountain, and filled the whole earth.