752. Courtyards That Extend into Enclosures

Shabbos 17:34

If one end of a courtyard extends between the walls of an enclosure made of corners, it is permitted to carry from the courtyard into the enclosure and vice versa. When two courtyards extend between the walls of the enclosure, carrying is prohibited unless an eiruv is made. If the well dries up on Shabbos, one may no longer carry within the enclosure. The Sages only permitted people to carry within such walls because of the water. If the well starts to flow with water on Shabbos, it becomes permitted to carry within the enclosure because an enclosure that is formed on Shabbos is considered valid. If the beam or pole at the entrance of an alley is removed on Shabbos, it becomes prohibited to carry in that alley even if it opens up to a carmelis.

Shabbos 17:35

If a portico is built in an open area, one may carry throughout its space even though it has only three walls and a roof. We consider the edge of the roof as if it descends and serves as a fourth wall. One who throws something into such a structure from a public domain is not liable; it’s like throwing something into a closed alley (i.e., one with three walls) that has a roof. If the corner of a house or a courtyard is breached and a gap of ten cubits (about 15’) is created, one may not carry within it at all. Even though an opening of ten cubits or less is normally considered an entrance, that is not the case here since entrances are not made on the corners. If a beam extends across the opening, we consider it as if it descends and closes the gap, rendering it permitted to carry within, provided that the beam is not slanted.