His statement: “Nor may he do any of that on a neighbour’s property or in a shared alley without the permission of those entitled to it.” The word “that” refers to everything mentioned previously: projecting a rawshan (projecting upper structure), a sabbāṭ (covered passage), a bench, and a waterspout. He may not do any of these on a neighbour’s property without his permission.
For example, if the wall of my house faces my neighbour’s property and I wish to construct a projecting upper structure, but my neighbour prevents me, it is prohibited for me to do so, because the airspace follows the ground. Thus, my neighbour’s ownership extends upward to the sky and downward into the earth. A covered passage is even more clearly prohibited, since it reaches the wall. The same applies to a bench and a waterspout: neither is permissible without his permission. May I open a window overlooking him?
This is permissible on condition that it does not overlook him, such as when it is high up. For if I am entitled to raise the wall to this height, then by opening a window I have merely raised part of the wall to that height.
His statement: “and in a shared alley”: this is the second type of alley, namely, the shared cul-de-sac. A non-through street is jointly shared by the neighbours, who are the ones entitled to it. Therefore, none of the four aforementioned structures—the projecting upper structure, covered passage, bench, and waterspout—may be installed except with the permission of those entitled to the alley. Those entitled are the people whose doors open onto that alley, not merely those whose houses are situated along it. Thus, one whose house is on the alley but who has no door opening onto it has no right in the alley. But if he has a door, he has a right in it. Therefore, these four things may not be installed except with their permission. If they grant permission, the right belongs to them; but if they do not grant it, then it is not lawful for him to do so. However, this differs from a through street in that any one of them