Moshe Gantz and Joseph Miller, founders of Kosherklaf.com, spoke with Arutz Sheva-Israel National News about their mission to educate the public on mezuzot, tefillin, and sifrei Torah - collectively known by the Hebrew acronym STaM.
Gantz explained that Kosherklaf “is a website that offers extensive information about mezuzot, tefillin, and sifrei Torah, including what defines different levels of quality, why one mezuzah may be of higher quality than another, proper mezuzah placement in the home, and how tefillin are made. Alongside this in-depth educational material, the site also sells these sacred items and more.”
To help promote the mitzvah of Mezuzah, kosherklaf.com is including a free copy of The Mezuzah User Guide by Rabbi Aryeh Lebowitz with any order of STaM.
Gantz went on to describe what inspired him to create the website. “I’ve had an affinity for the Hebrew language since childhood. I used to read dictionaries, and that love for the Hebrew language and its letters still exists today. Every Sunday, I speak in my synagogue, Young Israel of Woodmere, about a word in the weekly parashah. I’ve always had this deep love for Hebrew and its letters.”
Gantz also shared his background as a volunteer with Vaad Mishmeret STaM. “When I was at Young Israel of Hillcrest, we ran campaigns to check mezuzot and tefillin. During those campaigns in the 1990s, we discovered that over 70 percent of the mezuzot and tefillin brought in for inspection were possibly pasul (invalid). I decided to start a company that would educate people about the quality of mezuzot and how to be careful about what they buy, so they would purchase quality products. When I say 70 percent were pasul, most of those items were already invalid from the outset.”
Asked whether the problem stems from lack of care or lack of knowledge, Gantz said that in most cases it is simply a lack of knowledge. “You go to a store, buy a mezuzah, and rely on the seller to give you a kosher product. Many times, the seller doesn’t know either. People don’t realize the complexity and the details involved in STaM. That’s why we started Kosherklaf.com - to educate the public on what to look for and how to be careful.”
Co-founder Joseph Miller emphasized that education is especially critical in today’s online marketplace. “If you type ‘mezuzah’ on Amazon, you’ll see listings with thousands sold, many of which are printed on paper and, unfortunately, not kosher. While there are good online vendors, it’s not always clear who they are. That’s why we put education first.”
Gantz added that the goal is to help people understand what they already own. “If it’s something that can be improved, or something that wasn’t kosher to begin with, how can we help them? One common problem with tefillin, for example, is straps that are white instead of black, which makes them pasul. Many times, people think they purchased mehudar tefillin, when in reality they received low-quality items - sometimes even pasul ones. People often have no idea what they really have.”
He noted that an even more widespread issue involves mezuzah placement. “I personally checked over a quarter of a million mezuzot through house calls. When I started this business, I didn’t realize how prevalent this issue was: 95 percent of homes have problems with kvi’at mezuzah - the placement of mezuzot.”
Gantz detailed several common placement errors. “Sometimes a mezuzah is completely missing. Sometimes it’s installed on the left side instead of the right. Many people don’t know how to determine which side is correct. Another common issue involves sliding doors. In the US, sliding doors usually consist of one fixed panel and one moving panel. If the mezuzah is placed next to the fixed door because it’s technically the right side, it ends up too far from the actual opening, which is on the left - making it pasul. In Israel, most sliding doors have two moving panels, but that’s generally not the case in the US.”
He added that height is another frequent problem. “If the doorway is very tall and the mezuzah is placed at the standard height used for other openings, it may fall below the top third of the doorway, which also makes it pasul. In short, placement issues - including upside-down mezuzot - exist in roughly 95 percent of homes.”
Miller explained that Kosherklaf’s services are built in layers. “We’re trying to integrate both education and the sale of reliable religious artifacts. Our goal is that when you come to our website, you first gain a real understanding of STaM. We’re very excited to announce that, in partnership with Rabbi Ari Leibowitz - who is deeply passionate about STaM and mezuzah placement - we will be publishing a book that all customers will receive free with their order. The goal is to provide a deeper understanding of mezuzot and STaM quality.”
He said users can then explore the site’s listings and clearly see differences in quality. “Each product includes clickable explanations - not just visual comparisons, but detailed information about the parchment, quill, ink, the quality of the STaM, the sofer, and the relevant halachic requirements. We provide charts, articles, and explanations. We don’t want to overwhelm people, but we do want them to understand that there are real standards behind what’s being sold, with more information available for those who want it.”
Kosherklaf also provides follow-up support. “For questions about mezuzah placement or tefillin, we offer a WhatsApp help line. People send photos and ask whether something needs to be checked, whether it’s kosher, or how it should be placed. That option is conveniently available on our website,” Miller said.
For those particularly interested in STaM, the company runs a WhatsApp community that offers an inside look into the STaM world - from tefillin that are hundreds of years old, to fraud cases, to exceptionally beautiful examples of writing.
Gantz explained that there are three primary writing styles: Beit Yosef (standard Ashkenazi), Ari, and Sefardi. “For each style, we offer six quality levels. That means 18 options for mezuzot, and the same range for tefillin. When purchasing tefillin, customers can choose the writing style, quality level, tefillin boxes, and straps. Everything is presented with full transparency, so buyers know exactly what they are getting.”
He added, “Every set of tefillin we ship - whether in the U.S. or worldwide - includes copies of the parshiyot inside. Nothing is hidden. You can see exactly what you receive every time.”
Beyond online education, Kosherklaf brings STaM education directly to the public. Schools, yeshivot, and synagogues invite the founders to give hands-on classes covering topics such as ink production, the tefillin manufacturing process, bar mitzvah preparation, mezuzot, and more. Physical examples are brought so participants can see and touch STaM items and examine different writing styles up close.
Gantz concluded by highlighting a striking historical example. “We demonstrate why the Dead Sea Scrolls, written 2,000 years ago, are still readable today, while some Sifrei Torah or tefillin written just 100 or 200 years ago have ink that fades. We explain how ancient ink was made, why it endured, and why modern ink does not always last as long.”