A more thorough explanation:

Fall of the hammer is a term used in auctions to describe the moment when the auctioneer closes the bidding and announces the winning bid. Traditionally, the auctioneer would bang a hammer or gavel to signal the end of bidding.

For example, if someone is bidding on a painting at an auction, the auctioneer will say "Going once, going twice, sold!" and then bang the hammer to indicate that the bidding is closed and the painting has been sold to the highest bidder.

In some cases, such as online auctions, the auctioneer may not physically bang a hammer, but instead make a verbal announcement that bidding is closed.

Overall, the fall of the hammer is an important moment in an auction because it signifies the end of bidding and determines who the winning bidder is.