748. Walls at the Corners of Wells

Shabbos 17:26

If a beam is crooked, we treat it as if it were straight. If it is circular (so that a brick could not rest on it), we treat it as if it were flat. A circumference of three handbreadths (9”) is equivalent to a one-handbreadth diameter (3”). What if a beam is situated in the middle of an alley but it is crooked, causing a part of it to project outside the alley, above twenty cubits high (35’) or below ten handbreadths low (30”)? In such a case, we evaluate the distance that would be between the two ends of the beam if the crooked part was removed. If less than three handbreadths remains, there is one need not bring another beam. If more space remains, another beam must be brought.

Shabbos 17:27

If there are eight walls positioned at the corners of a well – i.e., two perpendicular walls at each corner – it is considered enclosed even if the open area is greater than that of the walls. Since there are walls on each corner, it is permitted for one to draw water from the well and to let animals drink from it. These walls must be at least ten handbreadths tall (30”) and six handbreadths wide (18”), and there must be enough space between the walls wall for two teams of four cattle each to pass, one entering the enclosure while the other exits. This opening may not exceed 13 1/3 cubits (about 20’).