A small square box, made either of parchment or of
   black calfskin, containing slips of parchment or vellum on which are
   written the scriptural passages Exodus xiii. 2-10, and 11-17, Deut. vi.
   4-9, 13-22. They are worn by Jews on the head and left arm, on week-day
   mornings, during the time of prayer.