The term Etz Chaim, (plural: עצי חיים Atzei Chaim), is also used to describe each of the wooden poles to which the parchment of a Sefer Torah is attached. A hymn including the aforementioned verse Proverbs 3:18 (Etz ḥayim hi lamaḥaziqim bah, v'tomkheha m'ushar) is sung in all Ashkenazi rites as the Torah is returned to the ark.
In Kabbalah, the Etz Ḥayim symbol (properly "Etz Ha-Hayim: The Tree of Life") is a mystical symbol used to understand the nature of God and the manner in which He created the world. The term Etz Ḥayim is also the title of one of the most important works in Jewish mysticism, written by Ḥayim Vital in the course of twenty years following the death of his master, Isaac Luria in 1572, presenting and explicating Luria's systematic reconceptualization and expansion of the insights of the Zohar and other earlier mystical sources. Vital's Etz Chaim is the foundational work for the later Lurianic Kabbalah, which soon became the mainstream form of Kabbalah amongst both Sephardi and Ashkenazi Jewry up to the modern period. This massive multi-volumed work circulated only in manuscript form amongst mystics for over 100 years, and was first published in 1782.
First volume of Hayim Vital's Kabbalistictext Etz Hayim has been translated in The Tree of Life: Chayyim Vital's Introduction to the Kabbalah of Isaac Luria – The Palace of Adam Kadmon, Donald Wilder Menzi and Zwe Padeh, Jason Aronson 1999. Introduction gives overview of Lurianic system