What happens when Rav and Shmuel get together, and disagree about a real-life situation in their midst? Also - 2 mishnayot that appear to be speaking broadly, where the Gemara narrows the cases. Specifically with regard to some basics about the spaces defined for eruvin. For example, if there's a large breach... Well, that's a basic case that we already know, so this must really be talking about something else. And also - a debate about how one week's status for an eruv and that particular Shabbat may (or may not) last for other weeks. For example, damage done to the corner of a house... And more from Rav and Shmuel.