Why is the Hebrew letter Shin on the front?
Shaddai, ("Almighty") is one of the biblical names for God. It also serves as an acronym for Shomer Daltot Yisrael, "Guardian of Israel's doors". The Mezuzah case should have an opening through which the word Shaddai is visible. If the casing is made of a material that does not allow for a window, then some feel the word shaddai, or the Hebrew letter shin must appear on the face of the mezuzah.
The Word Mezuzah Literally Means “Doorpost”
In Hebrew, the word Mezuzah means doorpost. The verse instructing us to hang a Mezuzah reads, “You shall write these words upon the doorposts of your house and upon your gates.” Talmudic literature applied the term to the scroll affixed to the doorpost, which is how we still refer to it.
The Mezuzah Is Placed on the Right Side
The Mezuzah is affixed to the right-hand side of the doorpost as you enter the room. For the front door, the right as you enter is always considered the right side. Inside the house, however, the right side is determined by which way the door opens. Whichever room the door opens into is considered the primary room, and the mezuzah is placed on the side that is on the right when entering that room.
The proper place for the mezuzah is at the bottom of the top third of the doorway. In other words, measure the height of the doorway and divide by three; then align the bottom of the mezuzah with the point two-thirds of the way up the doorpost.
It Is Hung Slanted
In Ashkenazic tradition, the Mezuzah is placed at a slight angle, with the top pointing toward the inside of the room and the bottom pointing toward the outside. In Sephardic communities, however, the mezuzah is affixed vertically.
Not Every Room Needs a Mezuzah
To properly fulfill the mitzvah, every room in your home or office—with some exceptions—should have its own mezuzah. Rooms smaller than 6.3 feet by 6.3 feet (e.g., a closet), bathrooms, or rooms lacking a doorway with two doorposts and a lintel do not need a Mezuzah.
The klef (scroll) of the Mezuzah
Each Mezuzah scroll contains the first two portions of the Shema, beginning with the verse, “Hear o Israel, the Lord is our God, the Lord is One.” Both of these selections contain God’s instruction to affix the mezuzah: “You shall write these words upon the doorposts of your house and upon your gates.”
It Has Shaddai Written on the Reverse
On the reverse side of the scroll, the scribe writes one of God’s names: Shaddai. The three letters of this name form an acronym for the Hebrew words Shomer daltot Yisrael,
The blessing said while hanging a mezuzah:
Transliteration: Barukh atah Adonai, Elohaynu, melekh ha-olam, asher keedishanu b'meetzvotav v'tzeevanu leek'boa mezuzah.
Translation: Blessed are you, Lord, our God, Ruler of the universe, who has sanctified us with God's commandments and commanded us to affix a Mezuzah.