Zayin is one of seven Hebrew letters, remembered by the mnemonic shatnez getz, that Jewish law requires a sofer to crown with three small decorative strokes called tagin whenever the letter appears in a Torah scroll, tefillin or mezuzah, a requirement recorded in the Talmud at Menachot 29b; the other fourteen letters, including its close neighbours vav and cheth, take no such crown, so a scribe copying a scroll must know by heart which seven letters this narrow rule applies to. Zayin's square-script form is also one of the letters most easily confused in a learner's early handwriting with vav and nun, since all three can be reduced to little more than a short vertical stroke with a small flag or hook, a resemblance that makes precise proportion, rather than any decorative flourish, the main safeguard against a scribal error serious enough to invalidate a word.
The letter's Hebrew name, meaning sword or weapon, appears already fixed in the older palaeo-Hebrew script that Jewish tradition holds the square Aramaic-derived alphabet replaced after the Babylonian exile, discussed elsewhere in this atlas, so the meaning long predates the letterform in current use. Zayin also appears as one of the plainest examples of a broader rule governing the seven crowned letters as a group: none of the seven shares an obvious visual feature that would explain the grouping on sight, and a scribe relies on memorised tradition rather than any pattern in the letterforms themselves to know which seven take tagin and which fifteen do not.