In response to an opening bid of 2NT, a bid of 3♣ asks opener to show his lowest-ranking four-card or longer suit (bidding 3NT if his only four- card suit is clubs). The partners may continue to show four-card suits in ascending order up to the level of 3NT. For many years, Baron over 2NT was a standard part of Acol but now most players use either simple Stayman or five-card Stayman.
