As I am sure everyone is aware, tefillin are holy articles (Heb: ‘tashmishei kedusha’), not far behind a ‘sefer Torah’ (Torah scroll). As such, extreme care must be taken, not merely that they do not become damaged or disgraced, but that they are treated with great respect at all times.
For example, tefillin may not be…
… hung on a hook (i.e. from their straps; however, if they are in their bag, the bag may be hung. Likewise, they may be placed on a shelf or cabinet that juts out of a wall, i.e. not resting on the ground – unlike a ‘sefer Torah’, for which these may not be done either.)
… left in a room in which a husband and wife sleep together, unless they are placed inside of another bag or covering, in addition to their regular pouch. … worn while eating. (Ed: Most authorities permit eating a little snack after davening, like if one intends to continue learning afterwards with tefillin.)
If someone’s tefillin fall to the floor (even in their bag), it is customary to give a few coins to tzedaka.
From here to the end of Hilchos Tefillin are halachos which are not as relevant today as they once were. For years, our practice has been to wear tefillin only during Shacharis. We all have safe places to store our tefillin, either at home or at the shul or Beis Midrash, and the important task of safeguarding our teillin are virtually a non-issue. In earlier times, when people wore their tefillin on the street, and they used public spaces for bathrooms, etc., many more questions arose which required proper guidance. As before, for these simanim, we will list the topics that are covered in the Mishnah Berura without going into detail.