Masonic tracing board with a Portal to another Dimension appearing between the pillars of Heaven and Earth.
There are three degrees of masonic tracing boards:
Initiate (first degree) – view of the Macrocosm and our place within and as part of it. Our limited physical existence and the various phases of spiritual development are represented as Ashlars.
Fellowcraft (second degree) – view of the crossing where physical world and spiritual truth meet, the point where without becomes the within. We can see a retrospect and prospect of our voyage to Knowledge; the reborn seed ripening into an understanding of Life which is at the centre of us all and at once the mystery of Natures Grand Circle.
Master (third degree) – shows us the inevitable point of transition between the physical and spiritual, from the finite to the eternal. Thing of the earth, mere physical labour and its results are transient, conjured from dust as mountains from sand and returnd by Time to the shore of the Eternal Waters from which we are all sprung.
Source: Freemasonry & Esoterica