This is the second book of the Mishneh Torah of the Rambam, Rabbi Moshe ben Maimon. Laws of the Sefer Torah, Tefillin, and Mezuzah.
This chapter explains how to write a Mezuzah and what happens if it was written haphazardly. It covers the law regarding worn-out Torah scrolls or Tefillin, whether they can be made into Mezuzahs, the spacing between sections of the Mezuzah, the crowns of each letter, the laws of writing, rolling, and affixing. It addresses who is obligated to bear a Mezuzah, whether it is an individual's or a public Mezuzah, and when Mezuzahs are inspected. It also covers who rents a house outside the Land of Israel and whether the obligation falls on the resident or the landlord.