Bava Batra

[The man who makes the wall] should smear it [with lime] on the outer side to the extent of a cubit. Why not on the inner side? — His neighbour will do the same on the outer side and claim that the wall is joint property. If he can do that, he can also scrape off the mark [on the outer side] and claim a share in the wall?  — Scraping is noticeable. [Suppose the partition is made of] palm branches, [how is he to make a mark]? — R. Nahman said: He should direct the points of the branches  outwards. Why not inwards? — Because then his neighbour may also turn points outwards and say that the fence is joint property.  If he can do that, he can also cut off the points [if they are outside] and throw them away? — [The other should therefore] smear clay over them. But even so the neighbour can come and scrape it away? — Scraping would be noticed. Abaye said [that for a partition made of] palm branches there is no security save by a written deed. IF, HOWEVER, THEY BOTH CONCUR. Raba of Parazika  said to R. Ashi: Let neither of them make a mark? — The rule is required for the case where one made a mark first, so that if the other does not do likewise, the first may claim [the whole wall] as his own. Is the Tanna then teaching us how to guard against rogues? — And is not the previous regulation also  a precaution against rogues? Raba replied: This is right and proper in the former clause:  the Tanna first states the law and then teaches how it should be safeguarded. But in the latter clause what law has he laid down that he should teach us how to safeguard it?  Rabina said: We are here dealing with a partition made of palm branches, and the object of the Mishnah is to exclude the view of Abaye, that for a fence made of palm branches there is no security save through a written deed. It therefore tells us that the making of a facing is sufficient. MISHNAH. IF A MAN HAS FIELDS SURROUNDING THOSE OF ANOTHER ON THREE SIDES AND FENCES THE FIRST, SECOND, AND THIRD, THE OTHER IS NOT BOUND [TO SHARE IN THE COST].  R. JOSE SAID: IF HE  TAKES IT UPON HIMSELF TO FENCE  THE FOURTH, THE WHOLE  COST DEVOLVES UPON HIM. GEMARA. Rab Judah said in the name of Samuel: The halachah follows R. Jose who said: IF HE TAKES IT UPON HIMSELF TO FENCE THE FOURTH, THE WHOLE COST DEVOLVES UPON HIM; and it makes no difference whether it is the encloser or the enclosed who does so. It has been stated: R. Huna said, [The contribution to the cost of] the whole must be proportionate to the actual cost of erecting the fence;  Hiyya b. Rab said, It must be proportionate to the cost of a cheap fence of sticks. We have learnt: IF A MAN HAS FIELDS SURROUNDING THOSE OF ANOTHER ON THREE SIDES AND FENCES THE FIRST, SECOND, AND THIRD SIDES, THE OTHER IS NOT COMPELLED [TO CONTRIBUTE TO THE COST]; which would imply that if the other fences the fourth side also, he must contribute [to the cost of the whole]. Now see the next clause: R. JOSE SAYS, IF HE TAKES IT UPON HIMSELF TO FENCE THE FOURTH, THE COST OF THE WHOLE DEVOLVES UPON HIM. This accords very well with the opinion of R. Huna who said [that he contributes to the cost of] the whole in proportion to the outlay on the fence; there is a genuine difference of opinion between the first Tanna and R. Jose, the former holding that the contribution has to be proportionate to the cost of a cheap fence of sticks, but not to the actual outlay, and R. Jose that it has [in all cases] to be proportional to the actual outlay. But if we accept the view of Hiyya b. Rab who said that it need only be proportionate to the cost of a cheap fence of sticks, what difference is there between the first Tanna and R. Jose? If he is not to give him even the cost of a cheap fence, what else can he give?  — If you like I can say that they differ as regards the hire of a watchman,  the first Tanna holding that he must pay the cost of a watchman  but not of a cheap fence, and R. Jose holding that he must pay the cost of a cheap fence. If you like, again, I can say that they differ as to the first, second and third sides, the first Tanna holding that he has to contribute only to the cost of fencing the fourth side, but not the first, second and third,  and R. Jose holding that he has to contribute to the cost of the first, second and third sides also.  If you like, again, I can say that they differ as to whether the fence in question must be built by the owner of the surrounding fields or of the enclosed field, [if the latter is to contribute to the cost of the whole]. The first Tanna holds that the reason [why the owner of the enclosed field has to contribute] is because the took the initiative [in building the fourth fence] and that is why the cost of the whole devolves on him, but if the owner of the surrounding fields took the initiative, the other has only to pay him his contribution to the fourth fence.  R. Jose on the other hand holds that it makes no difference whether the owner of the enclosed or of the surrounding fields took the initiative In building the fourth fence, in either case the former has to pay the latter his share of the whole. According to another version [of this last clause], they differ as to [whether the fourth fence has to be built by] the owner of the enclosed or the surrounding fields [in order to make the former liable for contributing to its cost]. The first Tanna holds that even if the owner of the surrounding fields makes the fourth fence, the other has to contribute to the cost,  whereas R. Jose holds that if the owner of the enclosed field takes it upon himself to build the fourth fence, then he has to contribute to the cost [of the whole] because he makes it clear that he approves of it, but if the owner of the surrounding fields builds it, the other does not pay him anything.