Reference for Eruvin 174:3
היו בראשו פירות אלו עולין מכאן ואוכלין ואלו עולין מכאן ואוכלין
If a breach to the extent of ten cubits was made in the wall, the tenants may prepare two 'erubs or, if they prefer, only one, because it is like a doorway. If the breach was bigger, only one 'erub and not two may be prepared'.<span class="x" onmousemove="('comment',' Supra 76b q.v. notes.');"><sup>4</sup></span> And when the question was raised, What is the ruling where it was not four handbreadths wide? ' Rab replied: 'The air of two domains prevails upon it and no object on it may be moved even as far as a hair's breadth'; whereas R'Johanan replied: 'The tenants on either side may carry up their food and eat it there',<span class="x" onmousemove="('comment',' But may not transfer objects from one courtyard into the other across that wall. Supra 77a.');"><sup>5</sup></span>