Carrying from One Domain to Another
4. [The following laws apply to] a private courtyard with a breach [in one of its walls] (1):
(a) If a section of the wall which is at least four "tefachim" (2) wide and ten "tefachim" high, remains on only one side [of the breach];
(b) At least one "tefach" of wall, which is ten "tefachim" high, remains on both sides of the breach;
and, in both (a) and (b) above, the breach is not wider than ten "amos" (3), it is not necessary to repair it [in terms of the laws of carrying in the courtyard on Shabbos]; this is because an opening of this nature is viewed, in Halacha, as an entrance ("pesach") rather than a breach.
If, however, the opening is wider than ten "amos" (4), or if neither four "tefachim" of the wall remain on one side of the breach, nor is there one "tefach" on both sides, and certainly if none of the wall remains at all, then, even if the opening is only three "tefachim" wide (5), it is forbidden to carry within the courtyard until the breach is repaired, preferably by erecting a "tzuras hapesach" ("form of a doorway") (6).
(1) A private courtyard surrounded by walls at least ten "tefachim" high is defined as a "reshus hayochid" ("private domain"), within which a person may carry objects on Shabbos. If there is a breach in one of the walls of the courtyard, and the breach has the dimensions defined in today's halacha, then the courtyard is redefined as a "carmelis," within which one may not carry objects on Shabbos (See Mishna Berura 361:6).
(2) Opinions among the authorities as to the exact length of a 'tefach' ('handbreadth') range between 8 and 10cm ( 3 to 4 inches)
(3) Opinions among the authorities as to the exact length of an "Amoh" ("cubit") range between 48 and 60cm (20 to 24 inches).
(4) If the breach is in a corner where a part of both walls is broken, even a breach that is less than ten "amos" must be repaired (See Shulchan Aruch 361:2).
(5) A breach which is less than three tefachim wide is, halachically, not viewed as a breach at all; in other words, it is viewed as if there was no opening there at all. This is based on the halachic principle called "Lovud."
(6) A "tzuras hapesach" will be defined in HY 82:6 coming in the next few days.