In a Jewish bar or bat mitzvah context, the leather prayer boxes used during weekday morning prayer are called tefillin.
Tefillin consist of two black leather boxes containing handwritten parchment passages from the Torah. One box is fastened to the arm and the other to the head using leather straps. The passages include the Shema and other verses that command remembrance of God and the commandments.
Traditional Jewish practice generally uses tefillin during weekday morning prayer, but not on Shabbat or most major festivals. Bar mitzvah preparation may introduce a child to the skills and customs connected with tefillin, although exact timing and practice differ among communities. Tefillin should not be confused with a tallit, which is a fringed prayer shawl, or a mezuzah, which is a parchment scroll placed on a doorway. The word tefillin is plural in Hebrew because the ritual uses two boxes.