Elmar is holding J♦ 9♦ and the flop comes 3♥ 7♣ K♦. He's completely missed the flop but has potential for a backdoor flush or straight. He checks and his rather timid opponent Jürgen has put in a half-pot bet. Elmar figures a float play might work here so he calls. The turn comes up A♦. Unless Jürgen has an Ace his float should work well now, so he puts in a half-pot bet (as his opponent is timid he knows this is a good sized bet). To Elmar's surprise Jürgen calls; he must have a very good hand. The river turns up a 2♦. Elmar has backdoored a flush! If he bets it might tip off Jürgen so he checks instead. To Jürgen this may just look like a busted straight draw, or perhaps a low set, so he puts in a small value bet. Elmar raises and gets called. Jürgen shows K♥ K♣ for a set -- he is of course quite distraught by Elmar's backdoor flush.