Defending Null

You are a defender and the declarer is playing Null, which means they have to lose every trick. Your only job is to force them into exactly one trick, any trick. There is no trump and no Augen to count. The cards run 7-8-9-10-Jack-Queen-King-Ace, each Jack stays in its own suit, and the Ten is no longer a high card here: it sits between the Nine and the Jack. Forcing always means the same thing: leading a card they hold nothing below. That is why your low cards are the tool and your high ones are not. Every lead, every follow and every discard below is aimed at that one moment.

Read the official rule on Null's card order.

Lead low from your longest suit

You're a defender against a Null and you're on lead. Play the lowest card of your longest suit. Low is the direction that forces: the lower the card you lead, the more of the declarer's holding sits above it, and length gives you enough low cards to keep rebuilding the pressure in the same suit. Hold five Diamonds with the Seven of Diamonds7 and the Eight of Diamonds8 among them, and lead the Seven. If they hold the Nine of Diamonds9 and the Queen of DiamondsQ there, they have to go over your Seven and will put down the Nine, their lowest. If your partner takes the trick off them with a higher Diamond, the game runs on, but the Nine is gone: the next time you are on lead, the Eight forces the Queen over it, and then they have nothing left there to duck with. Skip any suit they are already known to be out of, though: leading it only hands them a free discard.

Leading high to probe

You're a defender against a Null, you're on lead, and no suit promises you a force right now. Then leading high is an option too: your highest card in the suit where the most high cards are still out, or simply your highest card. A high lead forces only when the declarer holds nothing lower at all in that suit. Lead the King of HeartsK while only the Ace of HeartsA is still out above it: if their Hearts really is nothing but the Ace, they have to play it and the trick is forced. Usually they get under it, and even then the lead was not wasted, because whatever they duck with is spent. If they put down the Queen of HeartsQ, the card directly below yours, your lead has cost them their highest cover under the King. Taking your own trick costs you nothing here: Null counts no Augen, and you keep the lead.

Attacking a suit that already cracked

You're a defender against a Null and you have just watched the declarer duck in one suit. How close it was is the clue. If you led the Queen of SpadesQ and they got under it with the Jack of SpadesJ, the card directly below, then there was nothing left between your two cards, and that Jack is now gone. Lead that same suit again with the highest card you have in it: every lead costs them exactly one card they can duck under, and sooner or later there is none left. A single trick cannot prove it, because they may also have spent a high card deliberately just to be rid of it. Low leads out of your longest suit take their cover away faster anyway; leading high is the road for when you have nothing low left there.

Leading into your partner's void

You're a defender against a Null, you're on lead, and your partner has already discarded in one suit: they hold nothing there, while nothing so far says the declarer is out of it. That is the suit to lead, and it is where a high lead costs you least. The usual danger with a high card is that your partner has to follow and takes the trick off the declarer's card. If they cannot follow at all, that danger is gone: the trick comes down to your card against the declarer's, with nothing in between. A low card there would still force more often, because the declarer escapes it only by holding something lower still; what the void buys you is the freedom to spend a high card that was never going to force anything. Hold the King of HeartsK and the Eight of Hearts8 in Hearts and lead the King. If their Hearts is nothing but the Ace of HeartsA, they have to play it, and the trick stays with them: the game is over right there.

Following low

You're a defender against a Null, someone else has led, and you can follow suit. Then play the lowest card you're allowed to play. Losing the trick costs you nothing, because Null counts no Augen and defenders never need to win one. The real reason has two sides. If the declarer still has to play after you, your card sets the ceiling they must stay under: say your partner led the Ten of Clubs10 and you hold the Eight of Clubs8 and the Ace of ClubsA, then the Eight keeps the ceiling at the Ten and they need the Seven or the Nine there. Play the Ace instead and they can slip under with anything. If they have already played and were forced over the lead, say with the King of ClubsK, then your Eight stays under their card and the trick stays with them, exactly where you want it. What you are not doing is saving your high cards for a lead: leads are low, and high cards are no use for one.

Shedding a short suit

You're a defender against a Null, someone has led, and you have no card of that suit left, so you're blank in it and free to discard. Throw the highest card of your shortest suit. Hold only the King of SpadesK and the Queen of SpadesQ in Spades, and the King goes, the Queen next time, and after that you never have to follow suit in Spades again: every further Spade trick becomes a free discard for your next expensive card. High cards are no use as a low lead anyway, so you lose nothing by spending them in a suit where you were hardly ever going to force anything. Your longest suit is the one you leave completely alone: that is where your low leads come from, and you want to keep them as long as you can. Only when every suit you hold is the same length does that guard drop, and then you simply throw your highest card.

Forcing an open hand

You're a defender, the declarer is playing Null Ouvert with their whole hand face up on the table, and you're on lead. That ends the guessing. Look for a suit where you hold a card below their lowest one: they cannot stay under it, they have to go over, and that is exactly the trick you need. Say they show the Nine of Hearts9 and the King of HeartsK in Hearts while you hold the Seven of Hearts7 and the Eight of Hearts8: lead the Eight, your highest card below their lowest, because their answer is the Nine either way and the Seven stays with you for a second attempt. One catch remains. If your partner has to follow suit with a card above that Nine, the Ten of Hearts10 say, they take the trick away from you. So prefer the suit where nothing your partner could still be holding sits above the card the declarer is forced to play. The two cards nobody can see, the Skat or their own discards, count as your partner's here.

Stripping the declarer's cover

You're a defender against a Null Ouvert, you can see their whole hand, and no suit forces them yet. Then take the suit that gets there soonest, and simply count it out: lead your lowest card of a suit and the declarer answers with their highest card below it, and that card is gone for good. Say they show the Seven of Diamonds7 and the Queen of DiamondsQ in Diamonds while you hold the Eight of Diamonds8, the Nine of Diamonds9 and the Ten of Diamonds10: they duck your Eight with the Seven, and now the Queen is their lowest Diamond with your Nine sitting below it. Two leads. In Hearts they show the Seven of Hearts7, the Eight of Hearts8 and the Queen of HeartsQ against your Nine of Hearts9, Ten of Hearts10 and Jack of HeartsJ: the Nine strips the Eight, the Ten strips the Seven, and only then does the Jack sit below the Queen. Three leads. Diamonds is the shorter road, and you start there with your lowest card. It is a road, not a guarantee: only what you can do alone is counted. Your partner's cards and the order of seats can still shift the picture.

Following without spending your low cards

You're a defender against a Null Ouvert, their hand lies open on the table, someone has led, you can follow suit, and the declarer plays after you. Following low is right everywhere else, but here it can cost you the very card that would have forced them later. If they can stay under anything you're allowed to play, the trick is lost either way, and your card only decides which of theirs they get to spend: they answer under the highest card on the table by then. Say they show the Nine of Spades9 and the Queen of SpadesQ in Spades, your partner led the Ten of Spades10, and you hold the Eight of Spades8 and the King of SpadesK: put down the King. They duck with the Queen and keep the Nine, and your Eight forces that Nine on the next Spade lead. Put down the Eight instead and they duck with the Nine and keep the Queen, which your King can never get under: your force is gone. Keep the card that can still force, and spend the one that never could.

Discarding a card that can never force

You're a defender against a Null Ouvert, someone has led, you have no card of that suit left, and you're free to discard. Because their hand lies face up, you can see exactly which of your cards are worth nothing. If the declarer holds no Clubs at all, then no Club of yours can ever force them: they just throw something away on it. Neither can a card sitting above everything they hold in its suit. If all they show in Hearts is the Seven of Hearts7 and the Eight of Hearts8, they will always stay under your Ace of HeartsA, and that Ace will never force a trick. A card of a suit they hold none of goes first, then one above everything they hold, the highest of each kind first. You keep the low ones, which still have a job to do. Nothing dead in your hand? Then empty out your shortest suit as usual.