There are four astronomy parameters that are needed to be able to correctly apply the Z-axis rotation to the system, namely
and it is these four parameters that are being symbolised in the architecture of the antechamber which you can see by clicking here to overlay a drawing onto the screen.
The first stone, with the horizontal joint in it and the protrusion of stone, represents the epoch or date of the astronomy, and this stone is cemented in place inside the pyramid.
The other three stones, which have semi-circular cut outs above them, represent the three astronomy angles that are required and make up the theoretical locking mechanism that prohibits entrance to the main chamber. Because the lock is entirely theoretical these stones were never put in place. It is not possible to 'enter' the main chamber and understand its architecture fully without the exact angles that these stones represent.
The three stones of the theoretical locking mechanism do not exist inside the pyramid and there are no historical records of them ever being in place in the antechamber. The reason for this is that the angles that they represent also do not exist inside this pyramid, but can be found in the three subsidiary pyramids located next to the Great Pyramid.