My general understanding is that the takana if lechi (and korah) are specific to a "mavui". While a pas can be used to be matir a chatzer, and while a board of a mashehu may be either a lechi or a pas, they should not be confused. A chaver if mine suggested that it is just am issue of terminology, but that lechi in fact also Can be used as a Mechanism to effect heter in a chatzer;
Can you please provide some clarity? Thank you so much!!!
Moshe Rubin, Brooklyn, NY
1) The Gemara Eruvin 5b states that a Chatzer cannot be permitted with a lechi or a korah whilst a Mavui may.
2) The Mishnah 14b states that there is no lower limit to the breadth and thickness of a lechi required for a mavui, whilst for a chatzer the Gemara 12a states in the name of Rabbi Yochanan that the Pas must be 4 tefachim wide. A Pas cannot be a board of mashehu.
Chodesh Tov and Shabbat Shalom
1) It should be pointed out that despite the Gemara 5b that I cited above, a lechi can in fact sometimes give a heter to a chatzer. This is stated in the Gemara 12b that if the length of the chatzer is greater than its width, then the chatzer is considered as a mavui, and the Halacha is that a mavui can receive a heter from a lechi or a korah.
2) Possibly one could that argue that according to this the difference between a chatzer and a mavui is just an issue of terminology. However when the Gemara refers to a chatzer it is referring to the typical chatzer. Most chatzerot are wider than they are long, and conversely most mavo'ot are longer than they are wide.
3) Teshuvat Maharit #94 DH Ach Kasheh explains the difference between the Halacha for a Mavui and the Halachah for a Chatzer. For a Mavui all that is required is a "Heker"; it should be recognizable that the Mavui is not the same as the public domain oiutside. To achieve this it is sufficient to have a small lechi or korah and one already knows that the Mavui is not part of Reshut HaRabim. In contrast what is required for a Chatzer are mechitzot. This is why one requires a Pas of 4 tefachim for a chatzer since it is not merely a symbolic idea, but is like a Mechitzah.
4) This can be understood with the help of Teshuvat Rashba 5:203 who writes that a chatzer; which is next to only a small group of houses; is used for more private purposes, for instance eating there. Therefore it requires fuller walls since one does things there that one does not want everyone to see. A mavui is a more public place so it follows that it does not require such good walls, therefore a lechi or korah is suffisient.
5) If the length is more than the width, this means that it is more suitable for entrance and exit, not for private uses, but if the width is greater than the length, it is more suitable for personal things. This is why a chatzer which is longer than it is wide receives the din of a mavui, whilst a mavui which is wider than it is long receives the din of a chatzer.