Insertion & Stitching
The Biblical passages (parshiot) are inserted into the tefillin in the order that they are written. Each parchment is rolled from the end to the beginning, and wrapped in a covering made of parchment.
The verses and the covering are rolled in hair from a calf's tail.
One must be careful to insert the verses (parshiot) into the batim (boxes) easily, without pressure.
The next stage is to sew the batim with a tendon from a ritually-pure animal, backward and forward, so that there is stitching both above and below.
The final sealing of the batim is done by stitching, and not with glue.