This 4th-century manuscript of Virgil survives as only 12 whole or partial leaves, which are bound together with miscellaneous other fragments in a St. Gall codex. The fragmentary Virgil manuscript is one of only three extant ancient manuscripts written entirely in Square Capitals – a script which, on the basis of the surviving evidence, seems to have been used only for manuscripts of Virgil. Square Capitals are written in imitation of ancient inscriptional capitals and were never, as far as we can tell, in widespread use as a book script in antiquity.

Square Capitals are so called because of the letters approximate the square in their proportions, being in many cases almost as wide as they are high. The roundness of O, Q, C, and D, and the width of M and V, for example, lend the script its spacious, extremely regular aspect. The alternation of thick and thin strokes imitates the effect of chisel on stone. This example has proportions that are slightly taller than they are wide, but careful spacing between letters means that the overall effect reflects that of the highest grade of inscriptional capital. L and F are slightly taller than other letters; this is a regular feature of ancient capital scripts.

The manuscript is written in scriptio continua – entirely without spaces between words. The text is laid out in verse lines, which accounts for the ragged-right layout. (This was the normal practice in antiquity and for Latin verse throughout the Middle Ages. The meter helps the reader parse a line with no word spacing.) The only abbreviation used is Q∙ for enclitic -que. The running titles are part of the original preparation of the manuscript. The occasional apostrophe-like mark, which indicates a rhetorical pause, was added at an early date, but not by the original scribe of the manuscript. Various other apparent dots are actually areas of damage to the parchment.

The drypoint ruling is particularly visible under the first and last lines of writing.