past 20 years: promoting advanced women's learning and scholarship, promoting women's ritual inclusion in synagogue, promoting women's communal and religious leadership, and more. Women have been advancing change despite often vocal opposition by rabbinic leaders. Some Orthodox rabbis try to discount changes by claiming that women are motivated by sociological reason rather than "true" religious motivation. For example, Orthodox, Haredi, and Hasidic rabbis discourage women from wearing a kippah, tallit, or tefillin. In most Orthodox synagogues, women are not entitled to deliver divrei Torah-brief discourses generally on the weekly Torah portion-after or between services; shiurim are typically limited to men, as well. Furthermore, many Orthodox synagogues have physical barriers (known as mechitzot) dividing the left and right sides of the synagogue (rather than the usual division between the main floor and large balconies), with the women's section on one side, and the men's section on the other. Technically, a mechitzah of over four feet or so (ten handbreadths) suffices, even if the men can see the women, though it is not preferable. The mechitza serves to enhance the quality of prayer by ensuring that men are not distracted by the opposite sex. A typical mechitzah consists of wheeled wooden panels, often topped with one-way glass to allow women to view the Torah reading. Rules of modesty Although Judaism prescribes modesty for both men and women, the importance of modesty in dress and conduct is particularly stressed among women and girls in Orthodox society. Most Orthodox women only wear skirts, and avoid wearing trousers, and most married Orthodox women cover their hair with a scarf (tichel), snood, hat, beret, or wig. Rules of family purity In accordance with Jewish Law, Orthodox Jewish women refrain from bodily contact with their husbands while they are menstruating, and for a period of 7 clean days after menstruating, and after the birth of a child. The Israeli Rabbinate has recently approved women acting as yoatzot, halakhic advisers on sensitive personal matters such as family purity. Modern Orthodox Judaism Rabbi Joseph B. Soloveitchik, a leader of profound influence in modern Orthodoxy in the United States, discouraged women from serving as presidents of synagogues or any other official positions of leadership, from performing other mitzvot (commandments) traditionally performed by males exclusively, such as wearing a tallit or tefillin. A minor reason argued for why only men wear tefillin is that the tefillin help keep men from thinking