A well-dressed doorman wasn't the only person greeting visitors at Sotheby's Upper East Side location this weekend. Members of the auction house's art handlers union picketed the sidewalk all day Saturday and Sunday, brandishing signs that read, "Stop the War on Workers." The protest marks a dramatic turn in contract negotiations, which have been underway since May. On Friday, the 43 union art handlers, whose contract expired at the beginning of July, received letters telling them not to come to work on Monday. The auction house has locked out workers until the two parties can agree on a contract.