The Sukkah corresponds to the Torah:
A Sukkah has a similar shape to the letter Beis, and the Torah begins with the letter Beis. It is due to this reason that we find similarities between the structure of the Sukkah and matters in Torah. For example, its maximum height is 120 Tefachim, corresponding to the three times that Moshe went up to the heavens to receive the Torah, and corresponding to the years of Moshe’s life.. It likewise has a minimum dimension of 7 x 7 Tefachim, corresponding to the seven heavens.
 Maryu; Kaf Hachaim 639:12