Defense -- 3rd Hand Play
In this instructional article on defense, our partner will be leading to the trick (either the opening lead at trick one, or any trick later in the hand). It won't matter if it is a suit contract or notrump.
The old saying for defense is: "Second Hand Low, Third Hand High." In general, when playing third to the trick (on defense) play high. That covers more than half the battle, but unfortunately, there are exceptions and special situations. In this brief summary, I think it will be helpful to break it down into 4 situations as follows:
1) Dummy has low cards and partner has led a low card.
Or, put another way, you have a card higher than all the cards you've seen so far (your cards are all higher than dummy's cards and higher than the one partner led). In this case, play third hand high: For example:
Partner leads the 
3 and dummy has 1042. Dummy plays low and you hold any of the following:
A) AJ7 PLAY THE ACE
B) K85 PLAY THE KING
C) AQ PLAY THE ACE
D) J765 PLAY THE JACK
If partner leads an honor, like a jack or queen, and dummy plays low, and you have the ACE, you will typically win it. For example,
E) Partner leads the Q and dummy has 874 and plays low. Win your A if you have it.
F) Partner leads the J and dummy has 976 and plays low. Win your A if you have it.
Now, a slight exception to rule #1 :
2) If you have touching honors/cards, play 3rd hand "high," but with the cheapest in the sequence. For example, partner leads the 
4 and dummy has 865.
G) AK7 Win the king -- not the ace.
H) KQ10 Play the queen -- not the king
I) QJ109 Play the nine -- the cheapest in the sequence.
You will note that this is the opposite of the card you would play if you yourself were to lead the suit. Why? It has to do with helping your partner. It is a long answer, but trust me -- play the cheapest -- your partner will appreciate it. If you are my partner, and you put up the king as 3rd hand, I will "know" you don't have the queen--and that will help me out.
3) If dummy has the king, queen or jack -- and you have a higher honor, usually, you will withhold your honor and try to insert a "medium" or "in-between" card (hopefully, you were dealt one). For example:
J) Partner leads the 
4 and dummy has Q87 and plays low. You should insert the Jack from KJ3 or AJ3.
K) Partner leads the 2 and dummy has K105. You should play the 9 from AJ9x.
4) What if you don't have a card that might win the trick?
If 3rd hand can't beat dummy (let's say dummy' ace wins the trick, or the opening leader leads a high honor), a signal should be given. If you can't win the trick, the size of the small/spot card you play is meaningful. Though some players at certain times might signal count or suit-preference, the most important signal is ATTITUDE by far. Here is a summary of how to signal attitude if you can't win the trick (and partner has led to the trick):
Attitude Signal
This is by far the most important signal. It is used in two very important situations. One is when you discard, but that isn't the subject of this article. The other is when partner leads to the trick--so you are playing third to the trick. That is the subject of this article. If partner or dummy is winning the trick, tell partner your attitude. Play a high spot card if you like it, low if you don't. For example, partner leads a spade and dummy's ace takes the trick. Play the 8 if you have KQ82. Play the 3 if you have 843. *(Note -- see alternative methods in the footnote at the end).
Do not make attitude signals with cards above the 10. Don't signal with what potentially could be a trick. Of course, you won't always be dealt the right card to signal with.
*Note: There are many possible variations to what is shown here. There are many methods I like (such as upside-down). This is just intended as a mainstream summary.
Larry's Webinars on Defense
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updated June, 2016
