1. I am about to affix several mezuzos on multiple doorposts; how many blessings am I supposed to make?
In such a situation, one beracha is recited. This covers all the mezuzos which are affixed.
It is important not to speak about other matters until the completion of affixing all the mezuzos. If one became distracted with other matters at some point, a new beracha is required for the rest of the mezuzos.
2. On which mezuzah should I recite the blessing?
The beracha is recited on a mezuzah which is affixed to the doorpost of a room which is obligated according to all opinions.
The most common example of this is 1) an indoor room with 2) a floor and 3) ceiling, 4) surrounded by full walls, 5) with a door, and 6) an area larger than 7.5 x 7.5 feet, or 2.3 x 2.3 meters. [Fig. 1]
Often, bedrooms are the best qualifiers since family rooms such as living rooms and kitchens commonly do not have doors.
3. Do I recite the blessing before or after affixing the mezuzah?
If you are affixing the mezuzah with nails or screws, 1) hold the mezuzah case (with the mezuzah inside) against the wall, 2) recite the beracha and then 3) affix the case to the post.
If you are using “double-sided tape”, then 1) attach the tape to the case, 2) hold the mezuzah in hand near the post, 3) recite the beracha, and then 4) attach the mezuzah to the post.
4. What blessing is said on the mezuzah?
Baruch Ata Adonay, Elohainu Melech Ha'olam, Asher Kideshanu Be'mitzvosav, Ve'tzivanu Likbo’a Mezuzah.
5. Who should recite the blessing? Can I honor a relative or a member of my household with a blessing?
Ideally, the homeowner should affix the mezuzos and recite the blessing. Alternatively, an adult member of the household (man or woman) may affix the mezuzos and recite the blessing.
Absent these possibilities, the homeowner may appoint any adult Jewish male as his agent to affix the mezuzos for him. The agent should recite the blessing when doing so.
If the homeowner is capable of affixing the mezuzos on his own, it is preferable not to appoint an agent, nor to honor anyone else with the mitzva. Inasmuch as it is “his” mitzva, he should ideally perform it himself.
6. I bought a new mezuzah for my home. Do I have to recite a blessing prior to affixing it?
This depends on why you bought a new one. If the previous one was unkosher or missing, a beracha is certainly recited.
If you are merely replacing or upgrading what you assume was a kosher mezuzah, some halachic authorities rule not to recite a new beracha. However, the majority opinion is to recite a beracha in this instance as well. (The above rulings apply when the room needed a beracha in the first place. If however, the room does not have the requisite size or does not have a door etc. (see Q#3) no beracha is recited in any event.
7. I gave my mezuzah/mezuzos to a magiah (mezuzah examiner), do I have to make a new blessing when I reaffix it?
This depends on many factors.
All agree that if the doorway has been left overnight without a mezuzah, a beracha is required.
If, however, the mezuzah is re-affixed on the same day, there is a significant controversy as to whether a new beracha is required. The number of halachic authorities who maintain that a new beracha is indeed required even on the same day increases under any of the following circumstances.
a) If a significant amount of time elapsed from when the mezuzah was removed until the time it was returned to its doorpost. (I.e., it was removed at 9 A.M. and is being re-affixed at 6 P.M.)
b) If you took a nap (of half an hour or more) after the mezuzah was removed and before it was re-affixed.
c) If the mezuzah is re-affixed to a doorpost other than the one it came from.
d) If the magiah found a problem which rendered the mezuzah pasul according to some authorities – but was able to fix it. (If it was completely unkosher, a new beracha is obviously required since it is as though there was no mezuzah on the doorpost until this point.)
e) If the mezuzah had fallen off the doorpost (or was hanging by one nail) prior to being checked.
f) If the previous beracha on the mezuzah had been made by a prior tenant or owner.