Most of us were taught one trump rule early and never questioned it: you need eight. Eight cards between the two hands, or you don't call that suit trumps. It's a good rule. It is also, every so often, the reason you go down in 3NT while an expert pair at the next table cruises home in four of a major with only seven trumps between them.

That seven-card contract has a name. It's a 4-3 fit, sometimes called a Moysian fit after Sonny Moyse, an American writer who spent years arguing that a three-card raise wasn't a crime. He was mostly right.

What a 4-3 fit actually is

One hand holds four trumps, the other holds three. The defenders have six. That sounds thin, and compared with an 8-card fit it is: more often than not, one defender will hold four or more of those six, and when that happens you can't simply draw trumps and forget about them.

So why would anyone choose it on purpose?

Because the alternative is sometimes worse. Much worse. The classic case is a hand where you and partner have plenty of points for game, no 8-card major fit, and one suit that nobody can stop. Notrump is out; the defense will cash that suit before you take a trick. Five of a minor needs eleven tricks. Four of a major on a 4-3 fit needs ten, and the unstopped suit stops being a problem the moment someone can ruff it.

A hand that shows the idea

Picture South with ♠A64 ♥AKJ5 ♦KQJ ♣732, a balanced 18 count. North holds ♠KQ8 ♥Q73 ♦A6542 ♣94. That's 29 points between you. Game is obvious. The question is which one.

Look at clubs. You have five of them and not one honor. If you land in 3NT, the defenders lead clubs and keep leading them, and with eight clubs between them they will usually take the first four or five tricks. Down before you've started.

Now play four hearts. The defense takes two clubs, and on the third round North (the hand with three trumps) ruffs. South's four trumps are untouched. Draw trumps, run the diamonds, and ten tricks are there with room to spare. Same cards, same points. One contract is a near-certain minus and the other is a comfortable plus.

The rule that makes it work

Ruff in the short hand. That's almost the whole technique.

In a 4-3 fit your trump control lives in the four-card holding. Every time that hand has to ruff, it shrinks toward three, then two, and suddenly a defender with four trumps has more than you do. This is how 4-3 fits die: the defense keeps leading a suit you're void in, the long hand keeps ruffing, and by trick eight a defender is drawing your trumps.

So the ideal 4-3 contract has the three-card hand short in the dangerous suit. In the example above, North's doubleton club is exactly what makes four hearts sing. Give North three clubs and South two, and the long hand has to ruff the third round; the contract gets a lot shakier.

Timing matters too. Sometimes you want to draw two rounds and then stop, leaving a trump out while you cash winners. That's uncomfortable if you were raised on "draw trumps first," but it ties in with ideas from when to delay drawing trumps: the count of trumps isn't the goal, keeping control is.

When it's the wrong call

Plenty of the time. A 4-3 fit with weak trumps (say 8642 opposite J95) is asking for a 4-2 break to wreck you. If every suit is stopped, 3NT is usually better anyway, and the post on when 3NT beats four of a major covers why. And if the hand needs several ruffs in the long hand to come to ten tricks, forget it.

Good signs, roughly:

  • Strong trumps, ideally with the top honors split between the hands
  • The three-card hand is short in the suit the defense will attack
  • Your side suits are solid enough that you won't need to ruff in the long hand
  • Notrump has a genuine hole, not just a slightly nervous stopper

None of that is exotic. It's just judgment, which is exactly why players who follow the eight-card rule automatically never find these contracts.

How do you know if it was right?

This is the frustrating part at a regular home game. You go down two in 3NT, someone mutters about the club lead, and the next hand gets dealt. Nobody at your table ever finds out that four hearts was cold. You can't learn the lesson if you never see it.

Comparison changes that. When the same deal is played at several tables, the 4-3 fit shows up on the results sheet as a pair scoring +420 while three others are in the red, and suddenly it's a conversation rather than a shrug. That's what the same hand scoring differently at different tables is really about. Bridge@Home leans on exactly this idea: your table plays pre-dealt hands, and Bridge@Home lines your result up against everyone else who held those cards, so the "we should have been in four hearts" moments stop disappearing.

The takeaway

Eight trumps is a guideline, not a law. When notrump has an open suit and the minor-suit game is a stretch, look for four of a major with seven trumps, and check one thing before you commit: can the short hand do the ruffing? If yes, the strange contract is often the right one. The experts aren't being clever. They just counted.