Study Guide Eruvin 10 Today’s daf is sponsored by Rebecca Schwarzmer In memory of Toby Schwarzmer, Toibe Gittel bat Moshe Tzvi Hirsch z”l. Her love of Torah was evident in the way she lived her life, her career as an educator, her welcoming kiruv and her loving compassion. I was a granddaughter, not just by marriage, but in her heart. And by Onnie and Andy Schiffmiller in memory of Andy’s father, Tzvi ben Moshe Zeev and Frieda z”l. The gemara brings a question from a braita regarding the mishna about the small and large courtyards that put the measurements of each at 10 and 11 cubits. If that number was given, that would raise a question against the opinion that a post viewed from the outside but not the inside would work. The gemara explains why this would not work with that approach. In any case the gemara holds by that approach that it would work as a post even if not noticeable to the people inside the alley. In the mishna, it was stated that if the entrance to the alley is wider than 10, one needs to make the entrance smaller. Just as Rabbi Yehuda disagrees regarding the maximum height, does he disagree about this. If so, what is his limit? Can it be derived from laws about the barriers made around wells that are limited to 13 and a third? According to tanna kama, how does one fix a 20 cubit opening - is it enough to put up a beam in the center or is a proper a wall needed that juts into the alley by 4 cubits or goes along the opening of the alley to make the area smaller? Rav Yehuda gave an example of a 15 cubit space - one can add a wall of 3 and leave 2 cubits open at the end. This works because if the standing part is greater than the opening, we view it as if it were a solid wall. The gemara tries to make assumptions about how this principle would work if there were two beams together that covered a together greater amount of space than one opening - would that work? Can one assume it wouldn't since Rav Yehuda didn't bring that case? Several details regarding this principle are attempted to be derived from here but in the end are rejected. The gemara brings the case of a leather toilet cover regarding impurity as the hole is included in the measurement. Rav Dimi and Ravin debate the exact size of the solid sides and of the hole - do they debate in what cases two solid parts can override something empty as discussed above in the alley?