strong two clubs to show a very strong hand (usually at least 22 HCP). It could be argued that takeout doubles are conventional but their usage is so widespread that they may be considered a natural call. Classification Bridge conventions can be classified according to their purpose: Opening bid conventions Strong opening bids are used for hands stronger than the "normal" opening bid range (12-20 points in natural systems, 12-15/17 points in artificial systems) Strong two clubs in natural systems denote hands of 22+ high card points Benjamin Twos in natural systems Strong one club in strong club systems denotes hands of 16-17+ points Weak opening bids are used for hands weaker than the normal opening bid range, but with preemptive value: Standard preemptive bids, including "weak two" Bids Kamikaze 1NT Ekren Muiderberg Other opening bid conventions: Flannery Multi 2 diamonds Namyats Fit-seeking conventions are used in constructive bidding, in order to find a fit—a suit suitable to be a trump suit Baron Checkback Stayman Forcing notrump Jacoby transfers New minor forcing Stayman Bergen raises LTC Jacoby 2NT (also known as Stenberg 2NT) Slam-seeking conventions are used in constructive bidding to investigate the possibility of a slam contract Asking bids Blackwood Cue bids Gerber Grand slam force Last Train Quantitative notrump bids Relay bids Splinter bid Serious 3NT Defensive conventions or interventions are used to show a specific type of hand after the opponents have opened the bidding Takeout double Unassuming Cue Bid in reply to overcalls Lebensohl over weak two bids Defenses over 1 NT, including two- and multi-suited overcalls: Astro, Aspro, Asptro Cappelletti CoCa CRASH DONT Hamilton Landy Lionel Meckwell Multi-defense Multi-Landy Suction Two-suited overcalls over suit openings, like Copenhagen convention CRO Ghestem Leaping Michaels Michaels cuebid Raptor convention Roman two-suiters Unusual notrump Counter-interventions present a countermeasure after opponents' conventional and natural interventions: Lebensohl Negative double Negative free bid Rubensohl Unusual vs. unusual Other: Game trial bids Lightner double Texas transfer Regulations Under the rules of the sponsoring organization (for example national federations such as American Contract Bridge League (ACBL) and the English Bridge Union (EBU), zonal organizations, and the World Bridge Federation (WBF)), certain conventions are alertable, the partner of the player making the conventional call must say "alert" (or show an alert card from the bidding box) before the right-hand opponent calls. The right-hand opponent may ask the alerter about the meaning of the convention, or