He creates an eternal, tender image when he makes that final walk down the aisle with his Daughter or Daughter-figure, arm in arm towards her new life. He then steps aside for her husband to take over and he either sits in the front row or just stands to the side depending on the formality of the wedding.
As a result his main duty is unmistakable, which is basically to help and support his Daughter or Daughter-figure on her final passage from her single girl’s life to that of a married woman. By holding her hand and leading her up, he is also officially signifying that he gives his blessing on the union. 
