The Tfidanit was originally invented a company called Beit-El (which makes some other nifty tefillin accessories as well), before the imitations came along. To this day they maintain very high standards of product quality -- and have nice colors, too. But there's one little thing that's always bothered me: you have to put the Shel Yad on top of the Shel Rosh.

So what's wrong with that? Well, the Shel Rosh has greater sanctity, therefore you shouldn't place the Shel Yad on top of it.

When I was in the IDF two decades ago I used a very sturdy tupperware container, which was not so pretty and didn't have pockets, straps, etc. It did the job, but I was always wondering about that issue regarding the Tfidanit design.

A few weeks ago I came across that question online, answered by Rabbi Yerucham Erlenger. He brings opinions that permit it and opinions that don't, concluding that if it's needed to protect your tefillin, you can follow the lenient opinions, and under those circumstances all would agree that there's no lack of respect accorded to the Shel Rosh.

In a follow-up comment a reader notes that sometimes, depending on the size of your tefillin, you can lay the Tfidanit on its side, and then the issue apparently is resolved.

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