Diple was used in margins

Marginalia

Marginalia are scribbles, comments, and illuminations in the margins of a book.- Biblical manuscripts :Biblical manuscripts have liturgical notes at the margin, for liturgical use. Numbers of texts' divisions are given at the margin...

 to draw attention to something in text. It is sometimes also called antilambda because the sign resembles a Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 capital letter lambda

Lambda

Lambda is the 11th letter of the Greek alphabet. In the system of Greek numerals lambda has a value of 30. Lambda is related to the Phoenician letter Lamed . Letters in other alphabets that stemmed from lambda include the Roman L and the Cyrillic letter El...

 (Λ) turned upon its side. In some ways its usage was similar to modern day quotation marks and the so called French quotation marks (»

Guillemets

Guillemets , also called angle quotes, are line segments, pointed as if arrows , sometimes forming a complementary set of punctuation marks used as a form of quotation mark....

) are derived from it.

Isidore

Isidore of Seville

Saint Isidore of Seville served as Archbishop of Seville for more than three decades and is considered, as the historian Montalembert put it in an oft-quoted phrase, "le dernier savant du monde ancien"...

 remarks in his Etymologiae

Etymologiae

Etymologiae is an encyclopedia compiled by Isidore of Seville towards the end of his life. It forms a bridge between a condensed epitome of classical learning at the close of Late Antiquity and the inheritance received, in large part through Isidore's work, by the early Middle Ages...

(I.XXI.13) http://www.fh-augsburg.de/~harsch/Chronologia/Lspost07/Isidorus/isi_et01.html that diple was used to mark the quotations from Bible

Bible

The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

. He also talks about diple peri strichon (or sticon) which was used to draw attention separate concepts and diple periestigmene what was used to mark dubious passages (in this respect its usage was similar to obelos

Obelism

Obelism is the practice of annotating manuscripts with marks set in the margins. Modern obelisms are used by editors when blue-penciling a manuscript or typescript...

). Diple obolismene was used according to Isidore to separate sentences in comedies and tragedies, so its usage was similar to that of paragraphos

Paragraphos

Paragraphos literally meant in ancient Greek papyri anything that was written beside the main text, e.g. marginal note or sign to mark the close or beginning of a sentence. There are many variants of this symbol...

.