He then shifted to the heart jack, but no longer had an entry to give his partner a ruff in that suit.

East won with the ace and correctly gave her partner a ruff.

East took the heart ace and gave his partner a ruff.

It did not occur to East to return a diamond and give his partner a ruff.

For instance, one player can lead with the suit in which his partner is void so as to give a ruff.

West won and played a third heart to give his partner a ruff.

The game would probably have failed if East had been inspired to shift to a club, giving his partner a ruff.

He then played the ace and another diamond in the hope of giving his partner a ruff.

The best defense, following the diamond-king lead, would have been to shift to a club and later give East a ruff.

When West won, he could neither give his partner a ruff nor lead another trump.