The Sofer & The Halacha
In Judaism, there are four different types of ordination: Rabbi, Shochet, Mohel, and Sofer. A well–studied Rabbi may have the most all–encompassing knowledge of halacha. However, this alone does not render him fit to be a Shochet (slaughterer of kosher meat), a Mohel (able to perform a ritual circumcision) or a Sofer (Scribe). These three areas need a separate course of study to become ordained.
Safrus is unique among these three as it contains many more detailed halachos than Shechita and Milah. When sitting down to begin writing, the sofer must be able to recall all halachos pertaining to each and every letter as well as how to fit all of the letters together to form the columns vis–a–vis spacing, height and width, all of which are halachically mandated. There are also multitudinous halachos the sofer must know in regard to acts such as the writing of HaShem's name, fixing letters that were written incorrectly, sewing the sections of klaf (parchment) together, all of which the sofer must be well versed in.
To a certain degree, a sofer should be able to answer any halachik shaylos pertaining to safrus that come his way for, this is how he knows to write it properly in the first place. But, as with any field in halacha, there are always questions that crop up here and there that need clarification from the leading poskim in the field. Having a Rav to take one's shaylos to is equally as important as any area of safrus.
The halacha states that the word "U'Chisavtam" (Devarim 6:9) denotes "Ksiva Tamma" or "clear/perfect writing". From here the sofer learns that his work is required to appear as beautiful as possible.
Ksav Mehudar is the term used in reference to the clearest, straightest, neatest form of writing that adheres to all specifications of halacha. Often we feel that, if we know nothing about safrus, we are at the mercy of the seller. While this may largely be the case, one can actually decipher the beauty of the writing simply by looking at what they have purchased. Just as regular handwriting can appear "sloppy" or "neat", so too can we observe among various grades of safrus writing. When the lines of the letters are written neatly and spaced out nicely, one clearly notices the higher grade of the writing. It is important to note however, that in regard to various letters, the halacha actually requires certain strokes of the letter to be slightly slanted. If one compares the letters seen in his purchase to that of perfectly written letters (such as can be seen here), he can easily tell how beautiful the writing in his purchase is.
Ksiva Im Kol HaHidurim
A "hidur" in hebrew refers to something that exemplifies extra beauty. This is gleaned from the principle of "Zeh Keli V'Anveihu" (Shemos 15:2). In safrus terms, this can be a detail such as not "cutting corners" when writing the letter. Rather, writing them as precisely as possible is essential. Another hidur, specifically in reference to writing HaShem's name, is for the sofer to go to the mikvah before doing so. Additionally, there are many things that the halacha states is "the preferred course of action but not absolutely required". Ksiva Im Kol HaHidurim indicates that all of these preferred stringencies are adhered to before, during and after the writing process.
Ksav Beis Yosef vs. Ksav Ar"i
Every mezuzah must be uniformed to 22 lines containing the first two paragraphs of the Shema, one underneath the other: "Shema Yisrael" (Devarim 6:4–9) followed by "V'haya Im Shamoah" (Devarim 11:13– 21). The standard writing sizes are referred by the length of the klaf they are written on. The most common sizes are: 6cm, 10cm, 12cm, 15cm, and 20cm. For more information on mezuzos see http://www.aish.com/jl/m/mm/48948731.html.
The Five Megillos
The following tables show the total number of columns in each Megilla based on the line count of each column:
|42 Line Column Length|
|28 Line Column Length|
|21 Line Column Length|
Megillas Esther, the most commonly purchased for personal use, has an additional option. The "smaller" version is according to the minhag of the Gr"a (The Gaon of Vilna, d. 1797) in which each column's length is 11 lines, totaling 38 columns.
A particular specification that some prospective Megillas Esther buyers request is what is commonly known as a "HaMelech Megilla". This is when all columns leading up to the list of the ten sons of Haman, all begin with the word "HaMelech". This is only possible for columns of 42, 28 and 21 lines and not the 11 line version.
The only variation for a Sefer Torah is in its writing size, not in its column length. According to today's custom, Sefrei Torah are uniformed in their 42–line column length totaling 245 columns (some total 248). As for the writing size, each Sefer Torah can range from very small to very large.
Tefillin are also uniform in their format. They contain four parshios each side by side: Kadesh Li Kol Bechor (Shemos 13:1–10), V'Haya Ki Yiviacha (Shemos 13:11–16), Shema (Devarim 6:4–9), and V'Haya Im Shamoa (Devarim 11:13–21).
There is one fundamental difference between the shel yad and the shel rosh. When giving the commandment to put on tefillin, the Torah states, "U'Kshartam L'Os Al Yadecha, V'Hayu L'Totafos Bein Einecha" – "Bind them as a sign upon your arm and let them be ornaments between your eyes." (Devarim 6:8). We extrapolate from here that the "Os" or "Sign", being singular, tells us that the four parshios of the shel yad should be written on one single piece of klaf. The one piece is then placed in the inner compartment of the shel yad. Conversely, "Totafos" or "Ornaments", being plural, tells us that the parshios of the shel rosh should be written on four separate pieces of klaf. These four pieces are then placed in their four respective compartments of the shel rosh.
The Sifrei Neviim (Books of the Prophets) are used in some shuls to read the Haftorah. See this chart of which books are read from on particular Shabbosos, holidays, and fast days (http://en.wikipedia.org/wiki/Haftarah#List_of_Haftarot).