[3] The klaf is prepared by a qualified scribe ("sofer stam") who has undergone training, both in studying the relevant religious laws, and in the more practical parts—i.e., carving the quill and practising writing.

The verses are written in indelible black ink with a special quill pen made either from a feather or, now quite rare, a reed.

In the Bible, the word mezuzah only refers to the two 'doorposts' or 'doorjambs' of a door,[4] the upright posts on either side of it which support the lintel, and appears in various contexts unrelated to any religious commandment or parchment.

[5] The word later acquired the modern meaning of piece of parchment in post-Biblical Hebrew due to the Deuteronomy commandment above requiring to write verses on doorposts.

[17] A culture-comparative analysis suggests that the objects placed on domestic thresholds often bear the function of an amulet repelling the broadly understood evil.

[21] According to various pieces of sociological research, approximately three-quarters of adults in Israel believe the mezuzah guards their houses.

[1] It is customary to write two inscriptions on the back of the parchment: Shaddai, ["Almighty"] one of the biblical names of God, also serves here as an acronym for Shomer Daltot Yisrael, "Guardian of Israel's doors".

The Sephardic custom (minhag) leaves out the phrase "כוזו במוכסז כוזו‎", and only the Hebrew word שדי‎ (Shaddai) is written on the back of the mezuzah.

Mezuzah cases are produced from a wide variety of materials, from silver and precious metals, to wood, stone, ceramics, pewter, and even polymer clay.

Generally, halakha requires Jews living in the diaspora (i.e., outside of the Land of Israel) to affix a mezuzah within 30 days of moving into a rented house or apartment.

For a purchased home or apartment in the diaspora, or a residence in Israel (owned or rented), the mezuzah is affixed immediately upon moving in.

Many observant Jews from all Jewish denominations have a qualified scribe check the mezuzot parchments for defects (such as small tears or faded lettering) at least twice every seven years.

In Karaite Judaism the Deuteronomic verse "And you shall write them on the doorposts of your houses and your gates" (Deuteronomy 6:9; 11:20) is interpreted to be a metaphor and not as referring to the Rabbanite mezuzah.

[45] On reading a news report of the mezuzah dispute, Chicago alderman Burton Natarus[46] drafted an amendment to the city's municipal code which made it illegal for a renter or owner of an apartment, house, or condo to be prohibited from "placing or affixing a religious sign, symbol or relic on the door, door post or entrance.

[56] In 2006, a woman in a condo building in Fort Lauderdale, Florida, was instructed to remove the mezuzah from her hallway unit and threatened with a fine.

[57] In Texas in 2007, a couple living in Houston was instructed to "remove the item attached to your door frame" to avoid violating association rules.

His bill to protect such religious displays, as introduced in 2009, was not adopted, but in June 2011 a slightly revised version (HB1278) was signed into law by Texas Governor Rick Perry.