Kilayim, Chapter Six, Mishnah Seven
This mishnah continues to deal with the laws of an aris.
1) An aris which turns away from a wall where it forms an angle, and comes to an end, they give it space to work it and they may sow the rest.
2) Rabbi Yose says: if there are not four cubits there, one may not bring seed there.
Section one: The mishnah describes a situation where an aris is planted at the corner where two walls meet, two of the vines being on one of the walls and three of the vines being on the other wall. In such a case, all he needs to do is leave six handbreadths from the vines in order to work them and he can plant the rest of the space in between the two walls.
Section two: According to Rabbi Yose, there must be at least four cubits between the two walls; if there is not he may not sow seeds there.