Demonstration, Part 5

Demonstration, Part 5

N
W   E
 
S
♠ K 8 6 5
♥ A 9 7 3
♦ Q 8 5
♣ 6 5

Dealer:

West

W N E S
1♣ 1♦ Double 3♦
3♠ End

If we double showing both 4-card majors, opener is able to compete over South's 3♦ with 3♠.