Specialized cuebid after an opponent overcalls. It shows either 5-4-4-0 or 4-4-4-1 with the shortage in the opponent's suit and at least 8-9 hcp. In some higher level auctions, the fit for opener's suit may be shaded down to 3.

For example, (hands are written with spades at top, hearts next, etc) x Part. RHO you Qxxx 1H 1S 2S this is the minimal amount Kxxx that you would have QJxx - 1H 1S 2S you would bid the same way KJxx with this hand, too! (But AJxx of course you wouldn't KQTxx allow a signoff...) x 1D 2S 3S here the auction is rather AJxx high, so the cue bid can JTx have shaded support QJxxx