Machon Ot - Tefillin - The Batim (Boxes)

The Batim (Boxes)

Tefillin are actually composed of a set of two Batim (Boxes): The box worn on the arm, called "Bayit Shel Yad", and the box worn on the head, called "Bayit Shel Rosh".

Shel Yad
The Bayit Shel Yad is smooth on the outside and contains one hollow cavity inside.

Shel Rosh
The Bayit Shel Rosh has three grooves along its length and four separate hollow spaces inside.

Tefillin, The Batim (Boxes)

In order to be Kosher, the Batim must be:

Colored black
Perfectly square on top
Perfectly square on the bottom
Contain square stitches
Contain grooves from the top to the seam (in the Bayit Shel Rosh)

Types of Batim
There are two main types of Batim:
1. Those made from cowhide ("Gassot")
2. Those made from sheepskin ("Dakkot")