[A CROSS-BEAM SPANNING] THE ENTRANCE [TO A BLIND ALLEY] AT A HEIGHT OF MORE THAN TWENTY CUBITS SHOULD BE LOWERED.
Uncommented on until now was the sentence which followed:
R. JUDAH RULED: THIS IS UNNECESSARY.
Although it has come up on previous pages, we have discussion now on width, not height, based on the conclusion of the Mishnah from page 2:
AND [ANY ENTRANCE] THAT IS WIDER THAN TEN CUBITS SHOULD BE REDUCED [IN WIDTH]
This “reduction” in the width of an entrance can occur with the use of side-posts. But it can get complicated when one courtyard or alley leads into another through a hole or breach. The side-posts might be flush from one perspective. And, although it is greatly argued, that matters:
it must be concluded [that a post that can be] seen from without but appears even from within cannot be regarded as a valid side-post. This is conclusive.
Similarly, a barrier might be erected in the middle of a 20 cubit wide entrance making two parallel “doorways.” Maybe it’s just a symbolic divider?
Levi learned: If [an entrance to] all alley was twenty cubits wide a reed may be inserted in the center of it and this is sufficient.
He himself has learnt it and he himself said that the halachah is not in agreement with that teaching
Instead a strip of boarding is constructed 10 handbreadths high by 4 cubits long and placed in the middle of the entrance parallel to the length – effectively creating two alleys.
Illusion and perspective: these matter!