may not move his door to a position nearer the entrance of the alley without the permission of the others. That is, if one of those who share the alley has his door at its beginning and wishes to move it to its far end, he may not do so, because he owns no more of the alley than the portion opposite his door and the portion nearer the entrance than it.

For example, suppose that this alley has six doors: two at its far end, two on the right, and two on the left. The owners of the doors at the far end have the right to open their doors anywhere along the alley, because they have a right in the whole alley.

As for the owners of the doors on the right and left, whoever is nearer the entrance of the alley may not move his door further inward without their permission. However, he may move it toward the entrance, because he has relinquished part of his right. But this is on condition that he does not open it directly opposite his neighbour’s door without his permission, for it may cause him harm.

May he open a ventilation window onto the shared alley?

The answer is yes: he may do so and does not need permission, because it causes no harm to the people of the street. Moreover, he has the right to lower his wall to the height of a man, so there is no objection to making ventilation windows.

“And he may not place his beams upon his neighbour’s wall except in cases of necessity, when he cannot roof [his building] except by means of it. The same applies to a mosque and other buildings.”

His statement: “And he may not place his beams upon his neighbour’s wall except in cases of necessity”: this is a new issue. Neighbours must necessarily have a wall between them, and that wall may either belong exclusively to one of them or be jointly owned. If it belongs to one of them, then it is his property; and if it is jointly owned, then it is