Even in the middle ages rings were exchanged during the wedding ceremony. Rings were made of gold or silver. The groom started the ring exchange by placing a ring on his brides thumb and saying, "In the name of the father." Then he placed the ring on his brides pointer finger saying, "and the son." He would then place the ring on his brides middle finger saying, "and the holy ghost." To end, he would place the ring on her fourth finger and say, "Amen." The ring would remain on that finger. The ring was left on the fourth finger because a vein runs from that finger to the heart, which symbolizes love. It was thought of as a sign of affection between them.
Amt, Emilie. Women's Lives in Medieval Europe.New York: Rotledge, 1993. (p. 86).