These Help pages can be downloaded here with the Winning Bridge Shareware game for Microsoft Windows 98, ME, 2000 and XP.
If you would rather read a book, take a look at the Help Index page for some suggestions.
Blackwood Convention
To use the Blackwood convention selected the Blackwood option in the Conventions Dialog.
The Blackwood convention allows a player to ask how many aces their partner holds.
To start Blackwood a player bids 4 no trump, their partner then bids:
0 or 4 aces: 5 clubs
1 ace: 5 diamonds
2 aces: 5 hearts
3 aces: 5 spade.
It is then possible to ask for kings by bidding 5 no trump with similar responses at the six level.