Rav Yehuda in the name of Shmuel rules that a mezuza written on two sheets or columns is invalid. The Gemara raises a difficulty from a braita that invalidates a mezuza written on two sheets only when it is placed within two separate sippin (doorposts), implying that if it were placed within a single post, it would be valid. The difficulty is resolved by explaining that Shmuel's intent was that even if it is placed in one post, the mere fact that it is "fit" or able to be divided between two posts renders it invalid, as a mezuza.

Regarding the determination of the right side in doorways between two rooms, Shmuel rules that one follows the "heker tzir" (the placement of the hinges). Rav Adda explains that this refers to the socket in which the door hinge turns; the side toward which the door opens is considered the primary room, and the right side is determined according to the direction of entry into that room. Rav Nachman instructed the Exilarch (Resh Galuta), who wished to fix a mezuza in his house before its construction was complete, that he must first hang the doors and only afterward fix the mezuza.

Concerning the manner of placing the mezuza, Rav Yehuda in the name of Rav invalidates a mezuza placed "k'min neger" (like a bolt), meaning like a horizontal bar inserted into the doorway. The Gemara raises a difficulty from the practice in Rabbi's house, where the mezuzot were placed "k'min neger," and resolves it by distinguishing between a completely vertical placement and a horizontal placement. It is further mentioned in this context that Rav Huna would fix a mezuza in the doorway between his house and the Beit Midrash even though Rabbi did not do so, because Rav Huna followed the practice of those accustomed to using that doorway, which renders it a doorway obligated in a mezuza.

In the matter of the mezuza's height, Shmuel rules that it should be placed at the beginning of the upper third of the doorway's height. Rav Huna disagrees, holding that the entire area of the doorway is valid, provided the mezuza is one handbreadth (tefach) away from the ground and one handbreadth away from the ceiling beam. The Gemara raises a difficulty against Shmuel from a braita and resolves it by explaining that Shmuel rules in accordance with Rabbi Yosi, who learns from a hekesh (textual comparison) between "u'kshartam" (tefillin) and "u'khtavtam" (mezuza) that just as tefillin are placed high up, so too the mezuza must be high up in the doorway.

Rava adds that the mezuza should be placed in the handbreadth closest to the public domain so that a person encounters the mitzva immediately upon entry. Rabbi Chanina adds a conceptual dimension: unlike a king of flesh and blood who sits inside while his subjects guard him from the outside, God guards His servants from the outside while they sit inside, as it is written, "The Lord is your guardian."

Additional laws discussed on this page deal with the requirements of a mezuza that depend on the structure of the doorway and the room. Rav Yosef in the name of Rava invalidates a mezuza that was recessed into the thickness of the wall more than a handbreadth. Rava exempts "pitchi shimai" (defective doorways) from mezuza; the Amoraim dispute whether this refers to a doorway without a ceiling or one without a proper doorpost. Similarly, an achsadra (portico) is exempt from mezuza because its posts are intended to support the ceiling rather than to create a doorway.

A gatehouse (beit shaar) that opens both to a house and a courtyard needs a mezeua on both entrances. However, a gatehouse that opens to both a house and a garden, the Tannaim dispute - and the Amoraim dispute the interpretation of their words - whether the obligation is determined by the entry to the house or the exit to the garden. Rav Ashi rules according to the stringency of Rav and Shmuel: any doorway used for entry into a house, even if it leads to an open space like a garden, is obligated in a mezuza.