Duchsustus is the name of a type of parchment

Parchment

Parchment is a thin material made from calfskin, sheepskin or goatskin, often split. Its most common use was as a material for writing on, for documents, notes, or the pages of a book, codex or manuscript. It is distinct from leather in that parchment is limed but not tanned; therefore, it is very...

 used for religious writings in Judaism

Judaism

Judaism ) is the "religion, philosophy, and way of life" of the Jewish people...

. It is originally a Greek

Greece

Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

 word and one of three Talmud

Talmud

The Talmud is a central text of mainstream Judaism. It takes the form of a record of rabbinic discussions pertaining to Jewish law, ethics, philosophy, customs and history....

ic names for animal skin. The other two are kelaf and gevil

Gevil

Gevil is animal hide that has been prepared as a writing material in Jewish scribal documents, in particular a Sefer Torah .-Definition of gevil:...

. The meanings of these terms, however, are the subject of controversy in Jewish law

Halakha

Halakha — also transliterated Halocho , or Halacha — is the collective body of Jewish law, including biblical law and later talmudic and rabbinic law, as well as customs and traditions.Judaism classically draws no distinction in its laws between religious and ostensibly non-religious life; Jewish...

. According to the Talmud, a sefer Torah

Torah

Torah- A scroll containing the first five books of the BibleThe Torah , is name given by Jews to the first five books of the bible—Genesis , Exodus , Leviticus , Numbers and Deuteronomy Torah- A scroll containing the first five books of the BibleThe Torah , is name given by Jews to the first five...

 should, ideally, be written on gvil, but may also be on klaf, Tefillin must be written on Klaf, and Mezuzah

Mezuzah

A mezuzah is usually a metal or wooden rectangular object that is fastened to a doorpost of a Jewish house. Inside it is a piece of parchment inscribed with specified Hebrew verses from the Torah...

 should be written on duchsustus, kelaf, or gevil. This instruction is dated to Moses

Moses

Moses was, according to the Hebrew Bible and Qur'an, a religious leader, lawgiver and prophet, to whom the authorship of the Torah is traditionally attributed...

 at Mount Sinai

Mount Sinai

Mount Sinai , also known as Mount Horeb, Mount Musa, Gabal Musa , Jabal Musa meaning "Moses' Mountain", is a mountain near Saint Catherine in the Sinai Peninsula of Egypt. A mountain called Mount Sinai is mentioned many times in the Book of Exodus in the Torah and the Bible as well as the Quran...

. Duchsustus is the animal's dermis

Dermis

The dermis is a layer of skin between the epidermis and subcutaneous tissues, and is composed of two layers, the papillary and reticular dermis...

, klaf is the epidermis

Epidermis (zoology)

The Epidermis is an epithelium that covers the body of an eumetazoan . Eumetazoa have a cavity lined with a similar epithelium, the gastrodermis, which forms a boundary with the epidermis at the mouth.Sponges have no epithelium, and therefore no epidermis or gastrodermis...

, and gevil is both layers tanned unseparated.