Identification System to Distinguish between Rashi and Rabbeinu Tam Tefillin

Distinguishing Between Rashi and Rabeinu Tam Tefillin

It is the widespread custom for men to don two pairs of tefillin: one with the four parshiyos (the selected portions of the Torah written on scrolls of parchment) in the order prescribed by Rashi (i.e. the portion of Shema before V’haya im shamoa), and the other pair in accordance with the opinion of Rabeinu Tam (V’haya im shamoa before Shema). 

The tefillin shel rosh (placed on the head) are easy to tell apart as there are hairs protruding on the front of the bayis (the box encasing the parshiyos) to the right of the parsha containing V’haya im shamoa: On the Rashi tefillin that is between the third and fourth sections of the bayis, and on the Rabeinu Tam tefillin it is between the second and third sections (i.e. in the middle).

However, the tefillin shel yad (bound on the arm) are indistinguishable on the outside. Some poskim mention the custom of making the bayis of the tefillin d’Rabeinu Tam slightly smaller in order to tell them apart; however, that is not the common practice. In order to avoid confusing the two, it’s advisable to make some kind of indication on the protective box which covers the tefillin shel yad, or to cut the end of one of the retzuos (tefillin straps) in a way that will differentiate them. Of course, no mark should be made on the tefillin themselves. #451

https://halacha2go.com?number=451

Practical Halacha: One minute a day. By Horav Yosef Yeshaya Braun, shlita, Mara D'asra and member of the Badatz of Crown Heights.