auctions are public sales of goods, by an officially approved auctioneer. He asks the crowd assembled in the auction-room to make offers, or "bids", for the various items on sale. He encourages buyer to bid higher figures, and finally names the highest bidder as the buyer of the goods. This is called "knocking down" the goods, for the bidding ends when the auctioneer bangs a small hammer on a table at which he stands. This is often set on a raised platfrom called a rostrum