Drury explained simply

Drury: general principles

This now well-established convention is used after a major opening in third or fourth position.

The 2♣ response (Drury) asks opener:
“Do you have a real opening hand or not?”

When should you use Drury?

1. With support for opener’s major and game ambitions

• With 3-card support
• With 4-card support

2. With a balanced hand of 11 HCP

• and a doubleton honor in opener’s suit