Q. In question 2280 you wrote that in a house where the basement is rented out to men, there is no prohibition of yichud (men and women secluding together) for the woman on the higher floor, if the door is locked from the upstairs side of the staircase and cannot be opened by the one in the basement. Since the woman has the key to unlock that door, why would there not be a prohibition of yichud for her, since she can always unlock the door going down?
A. Horav Shlomo Miller Shlit'a explained that the yichud concerns by nature, are mainly for the men to join the women and not the opposite. (See Kidushin 81a, Chazon Ish E.H. 34:2, Divrei Malkiel 4: 120, Yad Halevi E.H. 18, et al; although some Poskim disagree, see Nitei Gavriel - Yichud 30: 2).
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit'a