60. Mezuzah

10:26 Tefillin are presumed to be fit for use inside and out so long as their boxes are in perfect condition. They need not be opened in order to inspect the parchments but it is appropriate to do so periodically because the possibility exists for them to be ruined by a person’s perspiration. If certain tefillin are only worn occasionally, they should be examined twice in seven years because they might have become moldy. If the box of tefillin breaks, the parchments must also be examined. They must also be inspected if they fell into water. If there isn’t anyone around who is proficient enough to inspect the tefillin and sew them back up, then one should wear the tefillin without having them inspected but he should not recite the bracha when he puts them on. (He wears them because they might still be fit and it’s his only opportunity to fulfill the mitzvah but he doesn’t say the blessing because they might not be fit.)

11:1
There is a mitzvah to put a mezuzah in every doorway in one’s house. This is the case even if he has many rooms and each room has several doorways, if a room is unused, or if people move out leaving some doorways unused. However, if one doorway is only used to bring in packages on an as-needed basis but another doorway is used for people to come and go, then the doorway used for packages does not require a mezuzah.