This is an offensive bid that shows the unbid suits,
rather like a takeout double by the defenders. Double of a major usually
promises at least 4 of the unbid 2nd major and at least tolerance for the unbid
minors. Some play that a double after a minor shows 4 of both majors. The direct bid of a major after opps bid
the other one therefore shows 5 or more in the suit. A partnership therefore may distinguish between 4 and 5+ card suits.
The number of points required to make a negative double vary, but the most common standard is 8 HCP (or a very good 7 HCP).
S: xx H: Ax D: xxxxx C: KTxx S: Qxxx S: x H: J10xx H: KQxx D: JTxx D: AKQx C: Ax C: Qxx S: AJTxxx H: xxx D: x C: QJ W N E S P 1C 1S X P 2H 2S 3H P/O