How were long vowels marked in some Latin inscriptions?

In classical Latin inscriptions, long vowels were occasionally indicated using specific orthographic devices to distinguish them from short vowels:

• Apex: An apex was a diacritical mark placed above a vowel to denote that it was long.1
• I longa: A taller variety of the letter i, known as i longa, was sometimes used in writing to indicate a long i sound as opposed to a short one.2