In Germany, engagement rings are traditionally being worn on the left hand. However, the wedding band is usually put on the right hand. After or even during the wedding ceremony, the engagement ring can be relocated to accompany the wedding band on the right ring finger.
More and more couples decide not to follow the traditional guidelines anymore. Of course, traditions are mere guidelines for orientation in this case. For example, it can be a lot more comfortable for left-handed brides to be wear their ring on the right hand. Often times, the abrasion also play a role in the decision: If the ring is worn on the less active hand, less wear marks are to be expected.