Why would there be a piece of retzuah in the compartment of the tefillin shel yad?

Question

Recently, I came across an old pair of tefillin peshutim of mine. They became un-fit for use years ago, and I have since replaced them with a sturdier pair, B''H. They aren't vintage, but they have seen better days for sure (peshutim don't hold up well in day-to-day use).

Understanding that they were a cheap pair, I was curious as to what the parchments looked like inside. I'd heard "horror stories" about cheap tefillin, and although I don't have the know-how to declare tefillin or mezuzos useable or not, I wasn't impressed with what I saw.

Anyway, when I opened up the tefillin shel yad and removed the parchment, something else fell out of the box. Upon inspection, I found that it was a small piece of cut retzuah (leather strap) that was stuffed in the compartment along with the parchment. I must say this was very unexpected.

I have never heard of any custom of putting a piece of retzuah in with the parchment. Why would there be a piece of retzuah in the compartment of the tefillin shel yad along with the parchment?

Answer 1

It is filler material to prevent the parchment from turning or slipping down and it is not a good idea.

R Yerachmiel Askotzky in his book Tefillin and Mezuzos writes (p. 89)

According to some poskim, loose klaf or a piece of retzuah should preferably not be placed between a parashah [klaf] and the wall of the bayit to prevent it from turning or slipping down, as it will separate between the parashah and the majority of a wall or shin.

Instead, the matlit (the piece of parchment or animal skin that serves inside the tefillin boxes as a protective covering over the parshiot of the tefillin) should be made very long so that the excess can be used to make an accordion that will hold it it place.

Note: one cannot cut pieces from a used retzuah to hold the parashiot in place within the batim.

Answer 2

I realize this is an old question, but it caught my eye and I have a different possible explanation. Are you sure that the piece of retzuah was actuality in the compartment with the klaf? The reason I ask is that the sofer I use puts a small piece of retzuah in the Ma'abarta (the area that the retzuah is passed through). He does this to hold the retzuah in place so the knot stays against the bayis (many will tie a piece of sinew through the Ma'abarta and around the knot to achieve the same goal). It's possible that in your case this is where the piece fell from when you opened it, as opposed to from inside the bayis itself.