Early grain elevators and bins were often built of framed or cribbed wood, and were prone to fire. Grain-elevator bins, tanks, and silos are now usually made of steel or reinforced concrete. Bucket elevators are used to lift grain to a distributor or consignor, from which it falls through and/or conveyors and into one or more bins, silos, or tanks in a facility. When desired, silos, bins, and tanks are emptied by gravity flow, sweep augers, and conveyors. As grain is emptied from bins, tanks, and silos, it is conveyed, blended, and weighted into trucks, railroad cars, or barges for shipment.