## '''Entry''': The mezuzah should be put up on the doorpost which is to one's right upon one's entering the house. <ref> Gemara Menachot 33b, Rambam Hilchot Mezuzah 6:12, Shulchan Aruch 289:2, Taz 289:3, Levush 289:2, Aruch Hashulchan 289:5, Kitzur Shulchan Aruch 11:3, Kitzur Shulchan Aruch of Rav Mordechai Eliyahu 11:3. </ref> This criteria applies equally to the outer doors of the house to the rooms inside the house.<ref>Igrot Moshe YD 4:43:4</ref> For example, a room that only has one entrance obviously has the mezuzah placed on the right side going into the room.<ref>Ben Ish Chai (Ki Tavo, Shana Sheniya no. 6) writes that if there’s a room that’s a dead end then it is obvious that we put the mezuzah on the right going into that room. [http://www.yutorah.org/sidebar/lecture.cfm/788640/rabbi-hershel-schachter/the-laws-of-mezuzah/ Rav Hershel Schachter in “The Laws of Mezuzah” (min 34-42)] agreed. Based on the Maharil (responsa 94) regarding courtyards and balconies this rule is obvious. See below. </ref>
## '''Usage''': If a room has two doorways if one of the two rooms that it connects is used more frequently then the mezuzah should be put up on the right side going into the room that is used more frequently.<ref>
* The Levush 289:3 writes that the side rooms of a house which open to the main room which was warm in the winter should have a mezuzah going into the main room since it is used more than the side room. This rule trumps the direction of the door. This is accepted by the Shach 289:6 who comments that it is obvious. The Kitzur Shulchan Aruch 11:4, Chayei Adam 15:18, Chelkat Yakov YD 161, [http://www.yutorah.org/sidebar/lecture.cfm/788640/rabbi-hershel-schachter/the-laws-of-mezuzah/ Rav Hershel Schachter in “The Laws of Mezuzah” (min 34-42)], Igrot Moshe 4:43:4 and Hamezuzah Vehilchoteha 11:11 agree.
* The Chelkat Yakov YD 161 proves that the Mordechai is the source for the Levush. The Mordechai cited by Bet Yosef YD 289 writes that the gemara needed a doorway to resolve the question of a man's room and a woman's room next to one another because they are both equally used and open to the public. However, between a vestibule or foyer and the main room of the house that is used commonly certainly the mezuzah is placed going from the vestibule and the main room since it is used more. He adds that this is also true even if the main room is also open to the public and the vestibule is open to a courtyard.
* The Chelkat Yakov explains the Mordechai to mean to add that even though when the vestibule is open to a courtyard and the main room to the public people will use the vestibule more often as an exit than an entrance, nonetheless, since the main room is used more than the vestibule, we view the entrance between the vestibule and the main room as an entrance and not an exit. In this he is proving that the rule of majority of walking is trumped by majority of usage.