Bina represents pure bestowal, Hafetz Hesed. Bina can be situated in the head of the Partzuf and outside of it. Bina is not subject to restriction (Tzimtzum), and yet, she does come out outside because this allows her to endow the lower ones with her own attributes.
While being above the screen, Bina is blocked, locked inside the head. On the other hand, having gotten out, she performs bestowal to the lower ones, and everything they have they receive from her.
However, this “sneaking-out” doesn’t reflect on her in particular. While coming out, she doesn’t seem to have left the head at all and easily maintains communication with the upper Partzufim. Bina is free and may be present as Above, so below. Our salvation is possible thanks to this particular property of Bina.
From the 1st part of the Daily Kabbalah Lesson 12/2/10, The Zohar, Introduction, “The Buds”