- Is within three Tefachim from ground:[1] The wall must be within three Tefachim [23.5 cm.[2]] from the ground. Even if the wall is very high, if it is not placed within three Tefach from the ground, it is invalid.
[1] 630:9
[2] See Shiureiy Torah p. 249 that an Ama Dochakos is 47 cm. [as opposed to 48 for a regular Ama], and accordingly a Tefach Dochakos is 7.83 cm [i.e. 1/48 of a cm times 8, deducted from 8 cnetimeters] and by the Shiur Sukkah of 7×7 one should measure with the stringent approach of an Ama Sochakos, and the same would apply here Lechumra to measure the three Tefachim as Dochakos. See also M”B 633:2 and Shaar Hatziyon 633:2 that by Sukkah we follow the stringent approach in the dimensions, either Dochakos or Sochakos, and by the 7×7 dimension we follow Sochakos, and the same would apply here by three Tefachim; See also Midos Vishureiy Torah pp. 48-57 regarding Ama Sochakos and Dochakos; Piskeiy Teshuvos 633:1 writes that its 23.4 according to Grach Nah, when taking into account the Dochakos according to Chazon Ish, as he explains there in footnote 2
Other opinions-Chazon Ish: According to the Chazon Ish, the measurement is 28.26 cm following the 9.42 measurement of Tefach Dochakos. [See Piskeiy Teshuvos ibid]