Checking one’s retzuos
It is important to check periodically that the retzuos on one’s tefillin are still completely black and are not cracked or faded. The Mishnah Berurah rules that the entire length of the retzua must always be black (Biur Halacha 33:3 s.v. retzuos). (There are authorities who disagree, most notably Rav Yosef Chayim Sonnenfeld, who contend that it is adequate if most of the retzuah is black.) Also check that the retzuos are black all the way to their tip. Be particular to check that they are black near where the knot is tightened, because at that point the paint often rubs out. One should also check that the retzua is still wide enough near the knot and that the knot of the shel yad is touching the ketzitzah of the tefillin. If it is not, this can be corrected by a knowledgeable sofer.
While checking the retzuos, check that the batim, titura, and stitches are all perfectly square. This means that the width and the length appear to be the same length to the naked eye, and that there are no dents, nicks, or projections along the sides or in the corners of the bayis. The back corners of the batim often become rounded because of hats or taleisim that are constantly rubbing against them. By the way, the edges of the Ma’avarta do not need to be square.
If the stitch of the titura is not taut or it loops in the middle, it is not kosher, and you should contact your batim expert. With time or damage, the stitches often loosen or move, or the batim get banged or nicked and are no longer properly square. Your local batim expert has the equipment and know-how to repair them.
If the retzuos are no longer fully black, blacken them with kosher tefillin paint.
If someone’s retzuos are cracking in several places, he should consider replacing them.
Must the side of the retzua be black?
The side of the retzua that lies on the skin need not be dyed at all. There is an opinion that the edges of the retzuos should also be painted black (Keses HaSofer 23:2). However, this opinion is not accepted in halachic practice (see, for example, Mishnah Berurah 33:24 quoting Pri Megadim in Eishel Avrohom 33:7).
How wide are my retzuos?
The retzuos should be about ½ inch wide. When purchasing new retzuos, they should be wider, so that they remain the proper width even after they become stretched out.
How to maintain your tefillin
Maintaining your tefillin is fairly easy. Never leave your tefillin in direct sunlight, in a very hot place, or inside your car during the daytime. As much as possible, your hair should be dry while wearing your tefillin. Protect the corners of the batim by leaving the cover on the shel yad. (It should be noted that some poskim contend that one should not place these covers on the shel yad while one is wearing them or while making the bracha. However, since most poskim permit leaving these covers on, one may be lenient.)
Tefillin are one of the special signs that HaShem gave the Jewish people, and we should certainly excel in treating this mitzvah with the appropriate dignity.
