>>512745566
It is the Hebrew letter "shin."
It stands for the "sh" sound in Hebrew.
What they posted here >>512744393 is called a mezuzah, and it's in the shape of a B2.
>A mezuzah is a small parchment scroll inscribed with verses from the Torah, placed in a decorative case and affixed to the doorposts of Jewish homes.
>It serves as a constant reminder of God's presence and commandments, symbolizing a Jewish household and its commitment to Jewish law and tradition.
>The core of a mezuzah is a parchment scroll, handwritten by a qualified scribe, containing specific verses from the Book of Deuteronomy (6:4-9 and 11:13-21). These verses include the Shema, a central Jewish prayer, and the name Shaddai (God).
>The parchment is placed inside a decorative case, which can be made of various materials like wood, metal, glass, or plastic.
>The mezuzah is affixed to the right doorpost of each doorway (except bathrooms) of a Jewish home, usually near the top, with a slight slant inwards.
>A mezuzah signifies that a home is a Jewish dwelling, operating according to Jewish law and tradition.
>It serves as a visible reminder of God's presence and commandments, prompting reflection on Jewish values and practices.
>While not a good luck charm, it is believed to imbue the home with holiness and blessings, and can be a source of comfort and inspiration.
>The act of affixing and touching the mezuzah is a way to connect with God and express faith.
>The mezuzah fulfills the commandment in Deuteronomy to write God's words on the doorposts of the house.

The letter shin on the mezuzah case is reflective of the name of God, Shaddai, (שַׁדַּי) which is written on the back of the mezuzah parchment and begins with the letter shin. Shaddai means "Almighty."
in the letters of that name, shin, dalet and yud, it can also stand for the phrase “Shomer dalsos Yisrael,” or “Guardian of the doorways of the Jews.”