Threshing Floors were used in the ancient world to separate grain from the chaff. This was usually a two step process. First, the cut stalks of grain were spread on the threshing floor and a threshing sledge was pulled over the stalks by oxen. The sledge was a simple wooden sled or heavy board with stone or metal spikes on the bottom that would break the heads of grain from the stalks (Isa 41:15-16). The same thing could be accomplished by having the oxen walk over the stalks (Deut 25:4) or by beating them with heavy sticks (Judg 6:11).
The second step was to toss the broken stalks into the air with a large forked tool, usually made out of wood. The wind would blow the lighter chaff to one side, while the heavier grain would fall into a pile, which could then be gathered. This process of separating grain from chaff by wind is called winnowing (Ruth 3:2, Isa 30:24). Because of the need for wind, threshing floors were normally located on hilltops or in large open fields, and were often used as landmarks (Gen 50:10, 2 Sam 6:6) or meeting places (1 Kngs 22:10). Since threshing floors were so crucial to the life of the people, they were highly valued, and were often vulnerable to raids by bandits or rival tribes (1 Sam 23:1).
In this photo, the harvested grain stalks are stacked by the threshing floor awaiting threshing. This grain must have been freshly cut, because the stalks are usually spread out on the floor to dry before threshing to avoid mold. As can be seen from the worn stones in the center of the floor, this one has been in use for some time. While this threshing floor has been constructed at the edge of an open field, threshing floors in the ancient world were often carved directly into the rock.
Biblical tradition recalls that the site for the temple in Jerusalem was originally a threshing floor that David purchased from Araunah the Jebusite (2 Sam 24:18-23; or Ornan in 2 Chron 21:20-23). There are references in this account to the threshing sledges, the oxen, and even the already threshed wheat.
Because of the process of separating the good from the bad, threshing and winnowing became common metaphors for judgement (Dan 2:35), especially in the prophets (Isa 21:10, Jer 15:7, 51:2, 33, Hos 13:3, etc.). John the Baptist picked up this metaphor and used it as warning of the activity of the Coming One (Matt 3:12, Luke 3:17). Only rarely is the idea of threshing used metaphorically in a positive context (Joel 2:24).