וְהָיְתָה הָרֶשֶׁת, עַד חֲצִי הַמִּזְבֵּחַ
that the net may concentrate energy in the middle of the altar ... Shemot 27:5
The channel (tzinor) which collects Divine energy is actually an interwoven network of connected tzinorot (channels). Zohar describes the collecting tzinor as an inversion of ratzon (will). This means that, when the tzinor is closed (encircled), ratzon is detained through the act of a controlled tzimtzum (concentrating restriction) in order to receive light in the five-phased creaturely behina dalet of the human soul.
From the related dream of Mishpatim:
I had to help him survive the judging ordeal by gathering up all the balls (spheres like sefirot) which had been thrown out onto the gym floor and place them all within a high basketball hoop (the net closed at the bottom) within a short time-limited period of time.
As I put the the last ball into the high basket, the chamber opened up ...
Only in the independent human soul is the free will desire to receive Divine energy both restricted and realized simultaneously. Through the pentacle (enclosed pentagram) a witch receives Divine light. Through the pentagram, a witch channels that received according to her will.