Can I use a magnet to put up my mezuzah?
Well, yes, you certainly can use a magnet to put up your mezuzah, but we should probably add the question: “Is it kosher to use a magnet to put up your mezuzah?”
The traditional answer, according to halacha (traditional Jewish law) is no, it is not kosher to do so. The commandment is to affix (likboa, in Hebrew) the mezuzah, which requires that the mezuzah be attached so that it is effectively as permanent as possible, and in such a fashion so as to not come off easily. In fact, for the same reason, traditional practice would forbid the use of regular cellophane tape or Velcro. The mezuzah should be firmly affixed to the doorpost so that it will not fall off if it is lightly pushed, pulled, or bumped into.
It is worth remembering that, while it is the case that is actually affixed to the doorpost, it is the parchment inside that constitutes the actual mezuzah. Since that is so, according to traditional practice, strong glue or double-sided foam tape can be used if the case opens from the top or bottom, as the container is considered a single unit, fixing the actual parchment to the doorpost. However, according to halacha, a case which opens from the back should be affixed with nails or screws, since in such a case (pun intended), if glue or double-sided tape is used, it is only the back of the cover that is actually affixed, and the front, main hollow section which holds the parchment would not actually be affixed.
While there is no official Reform movement position on this particular matter, I would submit that most Reform rabbis (myself included) would respond that while it is better to affix a mezuzah more permanently, using screws, nails, glue, or double-sided tape, what is most important is that one places a mezuzah on one’s doorpost, especially the outside door leading into the home, and that if for some reason you would be reluctant to affix a mezuzah more permanently in such a fashion, but would be comfortable using a strong magnet, it would be far better to do so then not to have a mezuzah at all!
Learn more about traditions around the mezuzah from InterfaithFamily’s ebooklet, Mezuzahs: What’s On The Door?