Commentary for Eruvin 9:2

לא דכולי עלמא קסברי מותר להשתמש תחת הקורה ובהא קא מיפלגי מר סבר קורה משום היכר ומר סבר קורה משום מחיצה

differ on the following principles: One Master holds the opinion that a cross-beam [is required] on account [of the necessity for] a distinguishing mark;<span class="x" onmousemove="('comment',' That people might distinguish between the alley and the public domain into which it opens out, and would thus remember that what is permitted in the former is not permitted in the latter. A level of the width of one handbreadth which the residents must pass on their way from and into the alley is, therefore, quite sufficient for the purpose.');">⁶</span> while the other Master<span class="x" onmousemove="('comment',' Abaye.');">¹</span> holds that a cross-beam [is required] on account [of the necessity for] a partition.<span class="x" onmousemove="('comment',' Between the alley and the public domain. No partition is valid unless it is made for a floor space of no less than four handbreadths (v. infra 86b and cf. supra n. 9 final clause) .');">⁷</span> If you prefer I might reply that all agree<span class="x" onmousemove="('comment',' Lit., 'for all the world hold the opinion'.');">³</span> that a cross-beam [is required] on account [of the necessity for] a distinguishing mark; but here they<span class="x" onmousemove="('comment',' Abaye and R. Joseph.');">⁵</span>

Rashi on Eruvin