To strip a player of safe exit cards, so that when you put him on lead he cannot avoid conceding a trick.
As South, you play in 6♠ on a diamond lead. You win and draw trumps, stripping the opponents of safe exit cards in spades.
You next take the ace-king of clubs and a club ruff, stripping your hands of clubs, thereby making it unsafe for a defender to lead a club. When you then give up a diamond, whoever wins will have no safe exit cards and you avoid having to guess who has the queen of hearts.