A control bid is used to decide whether a slam has good prospects. A typical control bidding scenario arises when a partnership has established a fit and enough points for game. Now both players can show control of side suits, which protects against the opponents taking two tricks against a slam.Eg: Opener♠-♥AKT9832♦AK93♣J3Responder♠765♥QJ76♦76♣AKT91♥-3♥3♠= control bid3♠says "I am interested in slam, and I have control of the spade suit. Do you have a club control (clubs are the next highest ranked suit)?Responder would bid 4C to say "I can control the clubs", and now Opener can bid to 6♥ or 7♥ without fear of losing two club trucks.