Why Wedding Ring Should Put On The Fourth Finger??

You mean the ring finger? But even in these days of cardiothoracic science, it's not easy to put a ring around the heart. So in the old days they had a simple answer: they put the ring on the third finger which they believed had a vein, artery or nerve (a sort of a USB cable) running directly to the heart. And as the left hand is a bit closer to the heart than the right, they placed engagement and wedding rings on the third finger of the left hand. (Actually, during some periods in the past, the ring was worn on the right hand; a practice that continues to this day in some cultures, since the right hand is considered more righteous.) http://www.seiyaku.com/customs/rings.html