Study Guide Eruvin 5 Today's daf is dedicated by Sara Berelowitz in memory of her mother Kila bat Yehuda z"l on her yartzeit. She would have been delighted to know that her daughter is learning the daf. If the beam is higher than 20 cubits, by how much does one need to lower it? The gemara tries to understand what exactly the question is. Rav Yosef and Abaye each have their own opinion and the gemara tries to explain the debate between them. Four different answers are brought. The same question is asked regarding a case where the beam is lower than ten handbreadths - how far into the mavoi does the floor need to be lowered. Rav Yosef and Abaye also have a debate regarding this matter. Abaye brings two proofs for his position and Rav Yosef explains those sources according to his view. Rav Huna describes a case where the entrance to the mavoi has a partial wall jutting out - does one still need to put up a lechi there? It depends on the size of the wall. In the case that one would put up a lechi, where should it be placed? Rav Huna the son of Rav Yehoshua narrows the case of Rav Huna and doesn't require a lechi if the wall covers more than 50% of the opening as it can be derived from laws of courtyards by a kal vachomer. Some question whether this kal vachomer is valid, perhaps laws of mavoi are more stringent than courtyards?