Pictures If there are three houses next to each other situated in between two courtyards, how can one make an eruv? What if there were only two houses? If two courtyards have a window in between them, if the window is 4x4 handbreadths and within 10 handbreadths from the ground, we consider this an opening and then can make an eruv together. What if the window was a circle, what would be the circumference of a circle that would encompass a square of 4x4 inside of it? Rav Nachman said that the requirement that it be within ten of the ground would not be relevant in a house. What if there was a wall in between the two courtyards that was ten high and 4 wide? Does this prevent the courtyards from being able to make an eruv? What if the wall was breached? At what size is it significant?