Putting the parshiyot inside the tefillin and sewing the housings
1. Even if one had already checked the portions multiple times, he should check them once again, extremely carefully, before putting them in the housings, to make sure they are completely valid. He should also be very careful to put the portions of the shel rosh in order – that is, “Kadesh” in the outside compartment (the one furthest left from the perspective of the person wearing the tefillin), “Ve-haya ki” in the second, “Shema” in the third, and “Ve-haya im” in the fourth (the one furthest to the wearer’s right). Thus if one were to face the person wearing the tefillin, he would read the passages in the order in which they appear in Torah – “Kadesh,” “Ve-haya ki,” “Shema,” and “Ve-haya im.” If one alters this order, they are invalid. The left-handed person follows this same order, reading “left” and “right” like everyone else does [not reading “left” for “right,” cf. ch. 3].
2. Each portion is rolled from end to beginning, and wrapped with a little piece of klaf. The Rambam says wrapping thus with klaf is halakha from Moses at Sinai, but the rest of the posekim don’t think so, so if one omitted to wrap them, they are valid post facto if there are no other tefillin available. Everyone agrees that it is halakha from Moses at Sinai that they should be wrapped with a hair from a ritually pure beast; the practice is to wrap a hair around the portion, follow this with a piece of kosher klaf, and finish with more hair. Calves’ tail hair is generally used, to atone for the sin of the calf, but if one has no calf hair, one may use cow or ox – well-washed and clean. A little of this hair – shorter than a grain of barley – protrudes from the housing, preferably coming out by the portion “Ve-haya im” on the side nearer “Kadesh.”
3. Each portion is placed in its compartment so as to stand upright, so that the upper margin, the top line, is towards the top of the housing, and the lower margin is towards the opening, with the beginning of the portion towards the right hand of the reader (that is, one facing the person wearing the tefillin), so that if he opened them and read, they would be properly in order.
4. It is halakha from Moses at Sinai that tefillin are sewn with sinews from ritually pure beasts, as sifrei Torah are sewn – see ch. 17 pp. 1,2.
5. We have already seen that it is halakha from Moses at Sinai that they are sewn in the form of a square, and one cannot be too careful about this. If the titura is made from leather other than that of the housing, one must be careful to sew the edges of the leather of the housing itself with the titura, and not the titura alone. People also put extra squares of leather, exactly the size of the titura, between the layers, to make the titura more substantial, and this leather must also be stitched in along with the titura and the edges of the housing.
6. One makes three stitches on each side, twelve altogether, but if one made more or fewer, say ten or fourteen, they are still valid. Some say that there should be a thread or a band between each of the compartments of the shel rosh, and so it is the custom to pass the thread between each of the compartments of the shel rosh.
7. There is an opinion which says that all twelve stitches should be made with one thread; some say that if it breaks one may tie it back together, and some say that if it breaks such tying is of no help since it shows that the thread was weak. If it was cut one may attach a new thread with which to finish the sewing, and if he has no other thread available, he may rely on the opinion which permits tying a broken thread.