What were Roman Capitals first used for?

Square capitals were used to write inscriptions, and less often to supplement everyday handwriting. When written in documents this style is known as Latin book hand. For everyday writing the Romans used a current cursive hand known as Latin cursive. Notable examples of square capitals used for inscriptions are found on the Roman Pantheon, Trajan's Column, and the Arch of Titus, all in Rome. Square capitals are characterized by sharp, straight lines, supple curves, thick and thin strokes, angled stressing and incised serifs. These Roman capitals are also called majuscules, as a counterpart to minuscule letters such as Merovingian and Carolingian.