1) The batim of the tefillin must be perfectly square. This applies to both the titura — the base of the tefillin — and the bayit — the cube that sits on top of the titura. If the titura or bayit was ruined in any way, such as if the edges were (a) chipped or (b) became crooked or (c) rounded,

one must show the tefillin to a qualified Rabbi or sofer who will determine whether it still meets halachic qualifications. Similarly, if the leather of the bayit tore, or if the tefillin somehow became soaked with water, it must be checked immediately given the likelihood that damage was caused to the writing on the parchment. If nobody is available to examine the tefillin, they should be worn but without a berachah.[175]

2) The surface of the entire bayit and titura must be black. If an area becomes white, it must be painted black. When painting tefillin one must have specific intention that he does so for the sake of the mitzva of tefillin, and he should verbally declare, לשם קדושת תפילין (“for the sake of the sanctity of tefillin”).[176]