Consider this deal from a previous Trumps Easter Teams event as the defender sitting West.
Your right hand opponent opened 1H, you passed, responder called 1NT (which, it is explained, may contain up to 11 points), your partner overcalls 2S, opener doubles this which is explained as takeout, you up the ante by bidding 3S, and North ventures 3NT. Here is the auction:
WEST NORTH EAST SOUTH
1H
Pass 1NT 2S Dble
3S 3NT Pass Pass
Dble All pass
Your double at the end (with the West cards shown below) is because you have hearts sitting over opener so that suit will surely not establish for them, and you also hope your double will tip partner off to lead a heart. Partner alas leads the DJ, and this is what you see:
NORTH (declarer)
WEST (you) EAST (partner)
♠ T752
♥ AJ95
♦ 64
♣ J92
SOUTH (dummy)
♠ 9
♥ T8432
♦ AQ53
♣ AK5
How do you plan to defend with the West cards? North's diamonds are the king and three small and declarer starts by cashing the four diamond winners, so your first decision is what to discard. You and partner are playing "odds and evens" signals so if you discard an odd card (especially a low odd) that encourages the suit, while an even card is McKenney (thus a low even card asks for the lower of the other two suits, a high even card asks for the higher of the other two suits).
Have you decided what to discard? And have you decided what to play when, later, a low heart is led from dummy? Here is the complete hand:
Dealer South, nil vul.
Contract: 3NT by North
NORTH
♠ K64
♥ K7
♦ K982
♣ Q864
WEST EAST
♠ T752 ♠ AQJ83
♥ AJ95 ♥ Q6
♦ 64 ♦ JT7
♣ J92 ♣ T73
SOUTH
♠ 9
♥ T8432
♦ AQ53
♣ AK5
On the third round of diamonds, West discarded the ten of spades, McKenney suit preference for hearts. This was a clear signal but, on this occasion, a fatal extravagance. Imagine instead that you as West discarded any other low card, such as the S7. After the four diamonds, declarer takes the A-K of clubs then leads a low heart.
Declarer is marked on the bidding with no more than a doubleton heart, presumably the doubleton king – hence the finesse, scrounging for an extra trick. West must not allow declarer to score that ninth trick. Rise with the HA, then lead the ten of spades to pin dummy's nine (leading a lower spade would allow declarer to duck the trick to East, who would be unable to profitably continue).
True, normally one leads low from an honour but sometimes you need to lead a higher card to trap declarer's honour. Bridge is often about following rules but it can also be about working out the right solution for a particular situation, as here. When defending a doubled contract, you can't afford to go off on holiday – even when it is Easter!