If two people are partners in a courtyard they shall build a wall in the middle of the courtyard, therefore if the wall collapses the stones and the place where the wall was built belongs to both of them. (1)
If the Minhag of the place is to build the wall with a certain type of stone or brick they shall adhere to the Minhag
If they build a wall out of Gvil (whole stones) each one must provide three Tefachim of the thickness of the wall and if they use Gazis (chiseled stones) each one must provide two and a half Tefachim.
If they build the wall out of half bricks each one must provide two Tefachim and if they use whole bricks each one must provide one and a half Tefachim.
If two partners own a garden if it is a place without a Minhag they shall build a fence in the middle, if they own a field in a valley in a place without a Minhag they are not obligated to build a fence.
If one of the partners of a field in a valley wants to build a fence he should build it in his property and make an indication on it that he built it and therefore if it collapses the stones and the place where it was built belongs to him.
If both partner of a field in a valley decide to build a fence they shall build it in the middle and make an indication on both sides of the fence and therefore if it collapses the stones and the place where it was built belong to both of them.
If a fence that separates a vineyard from a field of grain collapses we tell the owner of the vineyard to put it back up, if it collapses again we tell him again to put it back up if he gives up on it the produce is Kilayim and the owner of the vineyard is Chayav to pay. (2)
Rav says it is forbidden for a person to stand in his friendís field when the crops are fully grown. (3)
If the wall of a courtyard that is owned by two partners collapses they must rebuilt it to the height of four Amos, even if it was originally more than four Amos it is not necessary to build it higher than four Amos.
We force the partners of a shared courtyard to build a gate house and a door to the courtyard.
We canít force the partners of a shared courtyard to divide the courtyard between them unless each one will receive four Amos in the courtyard.
If someone builds a wall opposite the window of his friend it may not be built within four Amos of the window whether he is building it higher or lower than the window or next to the window. (4)
If a personís roof is next to the courtyard of his friend he must build a fence of friend Amos around the roof so that he canít look into his friendís courtyard.
A BIT MORE
1. Since the Chachamim require each partner to contribute equally to the wall if the wall collapses and one partner claimed that he was the sole contributor to the wall and it was built on his portion of the courtyard he is not believed even if the stones fell into his portion of the courtyard.
2. A distance of four Tefachim must be kept between the vineyard and the grain and otherwise it is Kilayim, however if there is a fence between them they both may plant right up to the fence.
3. Because he will give the produce a bad eye.
4. If he is building the wall higher or lower than
the window it must be at least four Amos higher or lower so that he canít stand on top of the wall and look through the window and if he is building the wall next the window he must build it at least four Amos away from the window so that he wont block the light from the window.