LEHO & HELO carding

There are many carding methods around, of which most focus either on showing count or on suit preference. Lots of experts like some sort of count, and lots of them hate it and swear by suit preference, because count gives away too much information to declarer. I'll leave that discussion for another time.

There are at least 2 methods which allow you to show both count AND suit preference with a single card! They're called LEHO and HELO, acronims for:
LEHO = Low Even High Odd
HELO = High Even Low Odd
They work best when playing UDCA or something similar, and when partner leads a suit where you have some length.

Suppose for the rest of the post that you're playing UDCA with LEHO.

Say you're defending 4♠, you hold ♦T92 and partner leads ♦Ace (apparently he wants to give you a ruff). You will discourage and/or show an odd number of cards, and you have 2 cards to do that: T and 9. Here comes LEHO in play:
- If you want the LOWEST remaining suit, you play an EVEN card (LEho)
- If you want the HIGHEST remaining suit, you play an ODD card (leHO)

So in our example:
- ♦2 would encourage partner to continue ♦.
- ♦9 asks for a ♥ switch.
- ♦T asks for a ♣ switch.

Important note: this is most useful in a long suit, so you might want to apply this only in a suit you bid.

A missed opportunity

Suppose you're playing with me and you hold the following hand:
♠ AKJT752
♥ A9
♦ 7
♣ 932

All vulnerable, your partner (= me) as dealer, imps scoring, the bidding goes:
pass - pass - 4♠ - 5♥
all pass

You may disagree with the 4♠ bid, but I like it.

I lead a ♦ and you take a look at following dummy:
♠ 83
♥ J8
♦ KQJ
♣ KJT765

Declarer wins with ♦J in dummy, and leads ♥J which you cover. Now the question arises: how can we defeat this contract? Imo there's a lot known about the entire hand.
- Your partner didn't lead ♠ which suggests he holds 2 or more (or 0, which is unlikely because declarer would hold 4♠ from the Q and wouldn't bid 5♥).
- He lead ♦, your short suit, which suggests that he's long in ♦, doesn't hold the Ace, but still wanted to give us a ruff.
- Declarer played ♥J, which suggests he holds either KQ or KT. Looking at the vulnerability, I'd rather give him KQ or even KQT, so there won't be another trump trick unless you can ruff.
So there are 2 suits left to try and reach partner for a ruff: ♠ and ♣. Looking at the auction and HCP alone, I think you shouldn't give partner ♣A. There's a lot more to say for ♠Q, since we think partner has 2+♠. Declarer can easily be singleton or void to explain his bidding. There's one more chance for success: partner having a void in either black suit.

So which suit do you play, and which card?

The key is in the lead: if partner played a high ♦, he says you can reach him with ♠, but if he lead a low ♦, he's asking for a ♣ return.

At the table, I held ♠Q96, declarer had a singleton. I lead a small ♦ instead of a high one, partner took ♥A immediatly but continued ♠K. After analysing this hand, I saw my error. Partner said he thought about a low ♠ at the table, but didn't do it because he hoped for another ♥ trick. I was glad he realised his argument for playing a high ♠ was wrong. We missed an opportunity to defeat 5♥, but I guess we learned from that mistake...