A Kosher Mavoy- Beit Shamai says: A lehi and a beam. Beit Hillel says: A lehi or a beam. Rabbi Eliezer says: two lehis. In the name of Rabbi Yishmael, said one student before Rabbi Akiva: Beit Shammai and Beit Hillel did not argue on a mavoy that is lower than 4 amot, for it is kosher with a lehi or a korah. About what do they disagree? On the width (of a mavoy) that is greater than 4 amot until 10 amot; Beit Shammai says it needs a lehi and a beam, and Beit Hillel says either a lehi or a beam. Rabbi Akiva says that they argued about both cases.