Defense against strong artificial openings

2C or 2D openings

• Pass: Any strong hand or weak but not suitable for obstruction
• DBL: Natural
• Overcall: Natural
• 2NT: 5+5+ in minors
• Other: pre-emptive

1C opening

• Pass: Any strong hand or weak but not suitable for obstruction
• DBL/1D/H/S: Natural
• 1NT: diamonds & spades
• 2C/D/H/S: the suit bid & and the next higher suit
• 2NT: clubs & hearts
• Other: pre-emptive

After 1C-1D and 2C-2D the structure is exactly the same, except that one cannot show clubs at the same level.

A bid of NT by the partner of the intervening player is the only forcing bid available.