What distinguishing feature identifies a driver's license for individuals under 21?

A driver's license for individuals under 21 is identified by its vertical orientation. This design choice helps to easily distinguish between licenses issued to minors and those issued to individuals who are 21 years of age or older. The vertical format is a clear visual cue that assists law enforcement officials, merchants, and others in quickly ascertaining the age of the license holder at a glance, ensuring compliance with age restrictions related to alcohol and other age-sensitive activities. This design strategy enhances public safety and facilitates responsible age verification practices.