While they may sound like the names of some of the Seven Dwarves, DOPI, ROPI and DEPO are actually conventional treatments designed to combat interference with Blackwood sequences.
DOPI and ROPI are better when the opponents’ suit is lower-ranking than yours, while DEPO is better when their suit is higher-ranking. Some examples will help. Say the auction goes like this, with your side vulnerable:
(2) Blackwood or Roman Key Card Blackwood.
The opponents are being pests, sacrificing in clubs or just trying to screw up your auction. How do you combat this? Since their suit (clubs) is lower-ranking than your suit (spades), DOPI is in effect. This means you double with zero aces (playing regular Blackwood) or zero key cards (playing RKCB) — that’s what the ‘DO’ part of DOPI means With one ace/key card you pass, which is what the ‘PI’ part refers to. To show more aces, bid the next suit available. 5♦, therefore, would show two aces if playing regular Blackwood or two aces without the ♠Q if you’re playing RKCB.
In this example, both sides are vulnerable:
This is similar to the first auction, but here right-hand opponent doubles 4NT instead of bidding 5♣. Some pairs play this way to tell their partners they want to sacrifice or that they want partner to lead his suit (clubs) without actually bidding it — usually because they’re vulnerable and they’re scared of being doubled.
Since you might just ignore this double and give the regular Blackwood response, it doesn’t cost them anything to play this way. You can try to stick it to them, however, by using ROPI. Redouble shows zero aces (‘RO’); if partner decides not to bid a slam after finding out you have zero aces, he might instead decide to take his chances in 4NT redoubled! He could, after all, have the ace of their suit or the protected king or even a tenace such as the ace–queen. The opponents might run to 5♣ which gives you the opportunity to double. Either way, you may well score better trying to nail the opposition.
The same is true if you pass to show one ace/key card (‘PI’). At matchpoints especially, you might decide to go for the top in 4NT (by your side) doubled or 5♣ (by them) doubled.
What if their suit is higher than yours? Say the auction is this, with your side vulnerable:
Since their suit is higher-ranking, DEPO is better. Double shows an even number of aces (‘DE’), pass shows an odd number (‘PO’). If you didn’t play DEPO, you would either be forced to guess whether to bid a slam which might not make or to double them when slam is cold. By doubling or passing, you get to stay on the five level, tell your partner how many aces you have and preserve the option of either bidding a slam or smacking the opponents.
Although the opportunity to use these treatments is rare, checking these boxes on your convention card may dissuade your opponents from interfering in your ace-asking auctions.
Do not Alert DOPI, ROPI or DEPO calls during the auction. In fact, most conventional calls in an ace-asking sequence are not Alertable. The reason is that it can pass unauthorized information to the Alerting side, “waking up” a player who has forgotten that they have agreed to play DOPI, ROPI or DEPO.
After the auction is over, you should explain the meanings of your calls to the opponents before the opening lead is made IF (big if!) your side declares just as you would for any ace-asking sequence.
What if we play 1430?
Some pairs prefer a variation of Roman Key Card Blackwood in which the 5♣ response shows one or four key cards and the 5♦ response shows zero or three. Pairs who play this way may prefer to play DIPO (double with one ace, pass with zero) and RIPO instead of DOPI and ROPI in order to keep their responses consistent.