The mitzvah of attaching mezuzot to our doorways derives from the Torah: “You shall write them (my commandments) on the doorposts of your house and on your gates” (Deut. 6:9, 11:20). Here are some guidelines for attaching mezuzot to your doorways:
1] A mezuzah can be affixed to the entrances of a home, and to any of its rooms used for living space which do not contain “filth”: therefore bathrooms, kitchens, attics, basements, storerooms do not acquire mezuzot.
2] The mezuzah should be placed on the upper third of the doorpost, as close a possible to eye level. It can be affixed through nails, screws or sticky pads. The mezuzah is fixed at an angle, with its top pointing inward. It should be affixed to a right doorpost according to the direction used most often to enter the room.
3] The klaf (“parchment”) bears two passages from Deuteronomy on one side, and the Hebrew word Shaddai (“Almighty”) on the other. The klaf is rolled and inserted into the case. Some people like to buy glass mezuzot and insert the scroll to display the passages of Deuteronomy through the glass, or the word Shaddai. In any case, photocopied parchments do not fulfill the mitzvah and should be discouraged. It is a mitzvah to purchase a genuine klaf from a professional Hebrew scribe to support scribes in their very sacred and ancient profession.
4] Standing at the entrance of a new home that is without mezuzot, one says the blessing:
Ba-rukh atta A-do-nai E-lo-hei-nu me-lekh ha-olam asher kid-sha-nu be-mitz-vo-tav ve-tzi-va-nu lik-bo-a mezuzah.
Then the mezuzah is attached to the door. She-he-che-ya-nu is then said:
Ba-rukh atta A-do-nai E-lo-hei-nu me-lekh ha-olam she-he-che-ya-nu ve-ki-ye-ma-nu ve-hi-gee-a-nu laz-man ha-zeh.
Other mezuzot may then be attached to internal doors without further blessings.
5] It is natural to think of the mezuzah as an amulet meant to ward off evil from one’s house. Many renowned sages have regarded mezuzot in this manner. But others interpret the mezuzah as a reminder to family members, going and returning from home, to keep God’s commandments in mind at all times. In Israel it has become common, particularly among taxi drivers, to hang mezuzot from rear view mirrors. Clearly this treats the mezuzah as a protective charm. We discourage this usage of mezuzot because Judaism is not a religion of magic, but a religion of pursuing God’s will.