Complex sentence: They can be worn on any finger, but those symbolizing pre-engagement are generally worn on the left ring finger; sometimes, the left middle finger or right ring finger is used instead to prevent confusion with an actual engagement ring.
Split into simpler sentences: They can be worn on any finger, but those symbolizing pre-engagement are generally worn on the left ring finger. Sometimes, people wear then on left middle finger or right ring finger to prevent confusion with an actual engagement ring.