Thatched fence

A few notes. 1. This of course depends on the location on the globe. 2. Of course, it is not required that this will be the source of the shadow at all times. This is a general, average assessment. 3. It is quite clear that these are supporting and not creative reasons, meaning that the halakha was known and the reasons came only afterwards to support it. The fact is that all of these explanations, for some reason, fall precisely within the 20-amemah limit (the Hanukkah violin and the Ka’movi). 4. If there is shade from both the sides and the canopy, it can still be okay. This is seen in the Gemara itself (“Del Ashterot Karnaim”), and the NEPAM of Rav Huna, Rav Amr regarding a large sukkah. 5. It seems that the halakha uses these criteria to define the orientation of a sukkah, but there is no requirement that the shade actually come from the thatch and not from the sides. In other words, the shade is a sign and not a reason. This is what some of the above-mentioned rabbinical commentary by Rav Huna says about a large sukkah (over 40 cubits), since in such a sukkah there is still shade from the sides but there is also shade from the thatch, at least partially. Regarding the explanation of the temporary dwelling, the Gemara later states this explicitly (that temporary is not really necessary, and it is only a sign and not a reason).