What feature is added to a minor ID in most states to indicate that it was issued to a person younger than 21?

In most states, a vertical format is added to a minor ID to indicate that it was issued to a person younger than 21. When an ID is issued to a person who is under the legal drinking age, it is often printed in a vertical orientation rather than the standard horizontal format. This serves as a visual indicator that the ID belongs to a minor and helps establishments and individuals easily identify individuals who are not of legal drinking age.
The specific features and design elements of IDs can vary by state, and some states may incorporate additional security features such as holograms, magnetic strips, or state seals to further enhance the identification and prevent fraud. However, the vertical format is a common feature used across many states to indicate a minor ID.