Question: If a Mezuzah cannot be affixed to the doorpost with nails or screws because the doorpost is made of metal, is it permissible to stick it on with strong adhesive tape?
Answer: The Torah commands us to affix a Mezuzah on every doorpost in one’s house. Let us now discuss the method of how to affix the Mezuzah: Must it be specifically nailed or screwed into the doorpost or can strong adhesive tape or glue be used as well?
The Rambam writes: “One should roll up the Mezuzah parchment from the end of the line to the beginning and place it in a tube or wooden holder. One must then affix it to the doorpost with nails or one may dig into the doorpost itself and place the Mezuzah in this hole.” The Rambam therefore states that the Mezuzah must be affixed well, either by means of nails or by placing it inside the doorpost itself. However, a weaker form of affixing the Mezuzah is insufficient since it is not really affixed to the doorpost. The Tur and Maran Ha’Shulchan Aruch rule likewise. The Mordechi writes in the name of Rabbeinu Shimshon that the Mezuzah must be affixed well to the doorpost; however, if one merely hangs it (from the doorpost), it is invalid since one has not truly affixed it. This is for the same reason we have mentioned above which is that a weak form of affixing the Mezuzah is not considered affixing at all.
Nevertheless, the Gemara (Menachot 34a) teaches us by expounding certain verses that the Mezuzah must be written on parchment. The Gemara further states that were we not to have expounded these verses and derived the Halacha that the Mezuzah must be written on parchment, would have thought that it is sufficient to engrave the words of the Mezuzah onto a rock and attach the stone to the doorpost. We can infer from this Gemara that writing the Mezuzah on a rock and affixing the rock on the doorpost poses no issue of a lack of affixing and is only invalid because ultimately, the Mezuzah must be written on parchment. Clearly, affixing a rock onto a doorpost or wall was done through cementing, masonry, or glue as opposed to with nails. Thus, we see that there is no obligation to affix the Mezuzah to the doorpost specifically using nails; rather, it is likewise permissible to do so using strong glue or tape (such as double-faced mounting tape), for affixing in this manner is also considered a strong affixing.
Thus, Maran zt”l rules in his Responsa Yechave Da’at that it is permissible to affix the Mezuzah using strong glue or adhesive tape, for the Mezuzah is certainly considered effectively affixed to the doorpost in this way.
