We established that trumping “ruffing” in the short trump hand (normally dummy) is an excellent way to make extra trump tricks. This is the process:
Note that the ruffing in dummy needs to be done before drawing trumps (unless dummy has four or more); draw trumps first and dummy’s trumps will be drawn too.
| 
					South Deals None Vul  | 
				
					
  | 
			||||||||||||||||||||||||||||||
					
  | 
				
					
  | 
				
					
  | 
			|||||||||||||||||||||||||||||
					
  | 
			|||||||||||||||||||||||||||||||
| 
					 East  | 
				South | West | North | 
| 2 ♠1 | Pass | 2 NT2 | |
| Pass | 3 ♠3 | Pass | 4 ♠4 | 
| All pass | 
					
  | 
			
	What happened
	Declarer beat West’s ♦ K with dummy’s ♦ A, and drew trumps. With 3-1 being the most likely division of four missing trumps, this took the expected three rounds...
And now the 4 ♠ game could no longer be made, with dummy now out of trumps. Declarer lost a diamond and, crucially, three hearts, at the end of the play. Down one.
	What should have happened
	There are fewer hearts in dummy than in hand, so a heart can be ruffed, provided you start early. Win ♦ A, and lead ♥ 3 to (say) ♥ Q and West’s ♥ A. West does best to switch to a trump, in an attempt to remove dummy’s trumps. Win ♠ 10 and give up a second heart. West wins ♥ 10 and leads a second trump. Win ♠ J and now, the extra trick, lead your third heart and ruff it with dummy’s final trump. Cross to ♣ K, draw West’s last trump, and merely give up a diamond at the end. 10 tricks and game made.
	If you remember one thing...
	Is there a side-suit in which dummy has fewer cards (0, 1 or 2) than you? If so, you can trump in dummy (but should do so a.s.a.p).