When the Blackwood bidder has a void, and partner shows one or more but not all missing aces, "asker" will not know whether partner's ace duplicates the void suit (where it would not be of great help) or covers side suit losers. For this reason cue bid to show aces explicitly, or Exclusion or Voidwood convention to ask for useful aces, is used with hands that contain a void. Often non-experts ask for aces when they really need other information from partner, acting act as if the convention is designed to ascertain whether the partnership holds all of the four aces or five key-cards. In fact the fundamental purpose should usually be to distinguish between lacking one and lacking two, because lacking two aces makes slam a bad bet. In other words, ace and key-card asking conventions should normally be used by one member of a partnership who plans at least to contract for 12 tricks if no more than one ace or key card is lacking. A simplified way to think about Blackwood is this: "I am concerned that we may lose the first two tricks, if we bid a slam. I can use Blackwood as a kind of insurance policy, to guarantee that this will not happen." But Blackwood will not help if, due to the structure of the hands, there are multiple ways to lose the first two tricks. It only helps, for the most part, if the exclusive risk of losing the first two tricks is due to the opponents' holding two cashable aces. Obviously, the opposition might hold the ace and king of a side suit, and could bang those tricks right down, resulting in an immediate set. Thus, a player should use Blackwood only when he can ascertain that the partnership holds at least second-round controls in all suits (kings or, if a suit fit is found, singletons). Thus, a Blackwood query by the player holding two quick losers in a side suit is a wild gamble, as it is still possible that the suit is not controlled by an Ace or a King. For the same reason, it is generally wrong to use Blackwood with a void. This is not always true, but the rule of thumb is: Don't use Blackwood with a void unless you are absolutely sure you know what you are doing, and why you are doing it. You may be missing two aces, but your void may compensate for the lack of one of the enemy aces. Thus, Blackwood will not tell you what you want to know: Are we at risk of losing the first two tricks? If your side has two aces and a void, then you are not at risk of losing the first two tricks, so long as (a) your void is useful (i.e., does not duplicate the function of an ace that your side holds) and (b) you are not vulnerable to the loss of the first two tricks in the fourth suit (because, for instance, one of the partnership hands holds a singleton in that suit or the protected king, giving your side second round control). Other problems can easily occur when a minor is the agreed trump suit, or the key suit when no trump suit is agreed. The reply to Blackwood could take the partnership past their agreed suit and going to the next higher level may be one trick too high. In these cases experts agree on using the Kickback or Redwood convention to save steps and be able to stop at 5 or 5. An alternative is to avoid using any type of Ace asking and use the cue bid alternative. A further problem occurs when, after hearing his partner's response, the player who bid 4NT wants to stop in 5NT as this is a forcing bid asking for Kings. A common agreement is that the first non-suit asks responder to bid 5NT. Whenever the first non-suit is a "queen ask", then the next non-suit asks to bid 5NT. This has to be planned in advance as if there is no such space partners have to bid a usually unmakeable slam contract.