Why is the Mezuzah Slanted?

Image: Mezuzah on the Zion Gate in Jerusalem (by Paul Arps, some rights reserved)

Recently I posted Why a Mezuzah? that looked at the various reasons Jews affix a mezuzah to our doorways. That gave rise to a good questions from a student in my online Intro class: Why is the mezuzah usually slanted?

It all goes back to a family debate and technical discussion. Rashi and his grandson Rabbeinu Tam disagreed about the proper way to hang a mezuzah. Rashi believed that the mezuzah should be upright, just as the Torah scroll is upright when it is properly stored in the Ark at the synagogue. Rabbenu Tam said, no! – the mezuzah should be horizontal, just as it is when it is laid on the table to read it.

We get this story from Rabbi Jacob ben Asher, the great Jewish legal writer. He writes in the Tur, his code of Jewish Law, that “careful people” will do their best to fulfill BOTH directions by placing the mezuzah on a slant. However, while that is the custom in the Ashkenazi world, Sephardim prefer to follow the ruling of Rashi and hang their mezuzot vertically.