Root Word "Sefer"

Why is it possible to purchase a Chanukah menorah-–but not a kosher mezuzah—at the local grocer’s?
How many sheets, columns and words are in a sefer Torah?
A sofer, sefer Torah, for kedusha (sanctifying)… Where do these words come from?

A sofer STAM is a scribe, not an author. On consecrated parchment, made from the back of a single calf, he copies into 245 columns, the 5,645 verses, composed of 304,805 letters that make up the Torah. The numbers and their calculation are significant. We call it tradition; in fact, the word sefer (book) comes from the root sfor: to count. It is no coincidence that seven weeks were counted from Pesach until Bnei Yisrael (the Israelites) received the Torah on Shavuot at Mount Sinai!

Every time a STAM writes, even if only to make a specific correction, a commitment to “sanctifying” is required : “I am hereby writing this for the sanctification of the sefer Torah/ megilla/ mezuzah.” Writing without expressly sanctifying will render the writing invalid even ex post facto, and one should note that a computer test cannot discern this, if, G-d forbid, it does occur.
Before inscribing Hashem’s (G-d’s) name, it too must be sanctified each time.

Therefore, in the Tikkun Sofrim (the book with the entire printed text), the book in every sofer’s mind’s eye and from where he reads and copies the words to be written, there is a special sign to remind him to sanctify the holy name.

A sefer Torah must be written on a scored parchment contiguous to the upper line (not to the lower as is usually done).

A great number of old sifrei Torah that undergo repair, as well as older small tefillin, were written on a specially treated parchment, recognizable by its extreme whiteness and shine. These Torah scrolls and passages for the tefillin are considered inferior as this process affects the durability of the ink. Why is this so? What exactly is this “treatment”?

Instead of investing in processing the parchment, to make it easier to write on, these parchments were smeared with a thick layer of lime which facilitated preparation. Writing on it was quick and it was pleasing to the eye. But lime is rigid, and when the Torah scroll was rolled, cracks would appear in the layer of lime and in the letters as well. This occurred even though the ink possesses some elasticity.

Recently, I was given a mezuzah, written on parchment treated this way from a hotel and, to my surprise, it turned out that the lime had peeled off and with it, the ink. It was obvious that the parchment had never even absorbed the ink, meaning that the writing had not been on the parchment as required. Mezuzot and tefillin as we know cannot be repaired, but a sefer Torah written on this type of treated parchment is also difficult to repair, and the repair will only last until the next time the scroll is rolled up. Therefore it is worthwhile to stay away from Torah scrolls written on this material, even after they have been restoration.
Buying mezuzot/ Chanukah menorahs at your neighborhood
grocery:

Though a Chanukah menorah, a tallit (prayer shawl) or tzitzit (fringes) are for use in a mitzvah, they themselves do not posses kedusha (holiness) and therefore there is nothing to prevent anyone from selling them.

On the other hand, a mezuzah, tefillin, etc., are comprised of sacred matter. In this case, one must know their source: who the sofer is and even who his customers are.