Shabbat 101: Boats and Little Goats

Can walls extend into the empty space near them to establish a private domain? The answer lies in the little goats who can run around in that space. Also: Ships that are tied together - carrying from ship to ship. And a challenge regarding the language of the mishnah - can it mean carrying from a large ship to another large ship, with a small one attached between them? Can these ships join together to make an eruv? Love and behold, boats can combine for this purpose. But can you do so on Shabbat? Note what appears to be a practical angle to this exploration of the parameters of the halakhah.