[thomaso]

This looks like it should be part of Coffin's Great 88, but I couldn't find it. South on lead with spades trump, needing three tricks:

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This actually came up when I was analyzing a double-dummy oddity deal.

Spoiler

The club lead forces west to ruff high, overruffed by the ace. Then north leads a diamond and east must ruff high, and south pitches anything, finally scoring the spade 9 because east is endplayed.

[rhm]

Trump promotions come in many guises. It is almost impossible to list them all.
The simpler ones can be foreseen and planned for.
The more complex ones usually occur by accident, typically after some cross ruffing scenario.
You have to work them out as they arise.

Rainer Herrmann