Mechitzah In Shul: Why And How?

 https://torah.org/torah-portion/weekly-halacha-5766-noach/#:~:text=*%20The%20mechitzah%20must%20reach%20the,of%20the%20mechitzah(18).

Harav M. Feinstein(10), however, after establishing that the basic requirement for separating men and women during prayer services is a Biblical obligation, holds that the basic halachah follows the second approach that we mentioned earlier. Although he agrees that it is commendable and praiseworthy to maintain the age-old traditional mechitzah, he nevertheless rules that the widespread practice of many shuls to lower the mechitzah somewhat is permitted according to the basic halachah. As long as the mechitzah is high enough to effectively block out any communication or interaction between the men’s and women’s sections, it is a halachically valid mechitzah. Accordingly:

* The minimum height for a mechitzah is shoulder-high, which the Talmud (11) calculates to be 17 to 18 tefachim high. Allowing for a difference of opinion concerning the exact size of a tefach, Harav Feinstein rules that a 66-inch mechitzah is permitted(12), while in extenuating circumstances 60 inches will suffice(13). Any mechitzah lower than that, however, is not considered a mechitzah at all.