Every Jewish home should make sure to have Mezuzos affixed to the doorposts. Those that already have Mezuzos affixed should have them checked (inspected) by a pious scribe to make sure they are made of parchment and are hand written and in no need of repair. The Divine Name SHA-DAI, on the outside of the Mezuzah, is an acrostic of the Hebrew words which mean "Guard-ian of the Doorways of Israel." According to the Zohar, the verse: "The L-rd will guard your going out and coming in, now and forevermore refers to the Mezuzah, which means that a Mezuzah guards the Jew both at home and outside until he returns. All the aforementioned matters protect not only the Jew who fulfills these Mitzvos, but also all the Jews wherever they are even those who have not yet fulfilled the Mitzvos. Although the fulfillment of a Mitzvah by one individual does not absolve another, and every effort should be made to see that a second Jew also fulfill them, still the fulfillment of these Mitzvos by each individual elicits a protection for the whole of the Jewish community for we are all interdependent-"All of Israel are brothers and we all have one Father." - The Rebbe - Bamidbar 5734