Reference for Bava Batra 123:6
איבעיא להו סיים לו את הקרנות מהו כמין גאם מהו
Rab, however, had [previously] admitted that if [the field in question] is bounded by those of Reuben and Simeon on one side, and by those of Levi and Judah on the other, since [if he desired to transfer only half the field] he should have written either '[the boundaries are the field] of Reuben [on one side and] opposite [to it the field of] Levi', or else '[the field] of Simeon [on one side and] opposite [to it the field of] Judah', and he did not do so, he meant to transfer all within the oblique line [from the end of Simeon's field to the end of Levi's].<span class="x" onmousemove="('comment',' The case dealt with here apparently is one in which the field is bounded on the north by those of Reuben (R) and Simeon (S), by each to half its length, and on the south by those of Levi (L) and Judah (J), by each to half its length, and the seller writes, 'the field that is bounded by those of Reuben and Simeon on the north and by that of Levi on the south', making no mention of Judah. (Fig. 3) The reading, however, is somewhat uncertain, and Tosaf. gives another explanation. ');"><sup>5</sup></span> If the field is bounded by fields of Reuben on the east and west and by fields of Simeon on the north and south, he must write, 'the field is bounded by fields of Reuben on two sides and by fields of Simeon on two sides.'<span class="x" onmousemove="('comment',' And not simply, 'it lies between the fields of Reuben and Simeon', as in that case half the field would suffice, v. fig. 4: ');"><sup>6</sup></span> The question was raised: If he merely marks the corners,<span class="x" onmousemove="('comment',' Suppose the field is bounded by a number of other owners' fields, some abutting on the corners, does he sell the whole or only two diagonal strips from corner to corner, v. fig. 5. ');"><sup>7</sup></span> how do we decide? If he draws the boundaries like a gam,<span class="x" onmousemove="('comment',' Marking a little of each side, in the shape of a Greek Gamma, thus: I' [Gandz, S., Proceedings of the American Academy of Jewish Research, 1930-32, pp. 37ff., connects the Hebrew term Gam with the Gnomon with the carpenter's square.] v. fig. 6. ');"><sup>8</sup></span> how do we decide?<span class="x" onmousemove="('comment',' Is this sufficient for the whole field, or does it convey only a diagonal strip? ');"><sup>9</sup></span>