"The hooks of the pillars"
Rabbi Yitzchak speaks here about the forms of the supernal pillars, Netzach and Hod, and the hooks from which are suspended the pillars below. The two pillars are united and watered, we are told, by the spinal column, Tiferet, that stands over them. Lastly, we learn that the hooks (vavim) are six within six, so that there are Vav's above in Chesed, Gvurah and Tiferet and Vav's below in Netzach, Hod and Yesod.
Essentially, this passage speaks of how Light flows. Tiferet is the upper Central Column, and Yesod is the lower Central Column residing between Netzach and Hod. This is the critical channel that needs to be opened for us to receive the Light. The Zohar now opens up Netzach and Hod, through the unifying power of Yesod, so that an abundance of Light floods our world, opening up the hearts of man to the true Creator.