Reverse Smith (against NoTrump)

Defenders against NoTrump contracts signal preference/dislike for the opening lead when following to declarer's first lead.
Reverse Smith against NoTrump applies only if declarer wins the opening lead.

Example

Assume a spade opening lead, won by declarer. Declarer then leads (trick two).
To that lead, defenders signal preference/dislike for spades (the trick one led suit) regardless of what suit declarer has just led.
They do, of course, have to follow with the suit that declarer has led.

If at trick one the 2 is led from T832 and the other defender plays the J, won by declarer's A, the opening lead defender does not know who has the Q.
Declarer may have won the A from an original AKQ9 in which case opening leader should probably postpone leading spades.
Declarer may have won the A from an original AK9(x) in which case opening leader might want to exit with a spade to other defender's Q.
Declarer may have won the A from an original AKQ(x) in which case opening leader might want to exit with a spade to other defender's Q9.

Similarly on another deal, opening leader may lead from Kxxx, the other defender following with the T [from either JT(xx) OR T(xx)].
Assume declarer wins the Q and makes a lead of another suit, won by opening leader.
If declarer originally held AQ, opening leader can lead away from Kxxx if first defender to next lead.
If instead declarer held AQJ, opening leader should probably postpone another lead away from Kxxx.
How can opening leader find out if the opening follower has the J?
Simple - by signalling preference (yes or no) to declarer's lead at trick two.

	NORTH KQ82 8743 QJ7 QJ
T6 AQJ5 AT64 852		J9753 K96 83 T73
	A4 T2 K952 AK964

Dealer: North Vul: Both MP Scoring

West

Pass
Pass
Pass

North
Pass
1
3N

East
Pass
Pass
Pass

South
1
1N
Pass

West led the

T.
Declarer won the first spade in dummy with the

K and tried to sneak a diamond trick by leading toward the

K.

West won the diamond and tried spades again.
South won in hand perforce the

A and cashed 3 rounds of diamonds.
Clubs divided and declarer ended with 2 diamonds, 3 spades and 5 clubs.

Why didn't East West score 1 diamond and 4 hearts setting the contract?

For many partnership, East might discourage a spade lead at trick one by playing a small spade (standard attitude: a high spade instead if playing upside down attitude).
However SOME partnerships choose a system of defence that signals count at trick one instead of attitude.

East, looking at 5 spades in hand and 4 in dummy, assumed 2+ for declarer's 1N rebid (West's leftovers of the spade suit numbering no more than two).
East could see there was no future in spades and could have so suggested, if playing Reverse Smith, that West try another suit when following to Declarer's first lead (a diamond).
With the 8 and the 3 to choose from, East would, playing Reverse Smith, show a dislike for the opening lead suit, spades, by playing the 8, the higher of the two diamonds.

Reverse Smith also applies for the Opening leader, who may have made originally led the

3 from as bad as

T43 or as good as

AQT3.
The other defender might need to know too.

Reverse Smith is a bit more popular than Smith perhaps because 'Upside Down Attitude' is more effective than 'Standard Attitude'.

Maybe RS is more popular because Smith is only one syllable:

"Do you play Smith?"
"When? Next round? Message for her?"

If you still play 'Standard Attitude', rather than Upside Down Attitude, you might prefer simply 'Smith' to conform to your habit.
If so, in the deal diagram above, to a trick two declarer diamond lead from dummy, if playing Smith (instead of Reverse Smith) East would play the

3 to discourage a losing West trick 3 spade lead try (rather than the

8).