I - The Antechamber
Article first time online: January 2010.
Reworked : May 2020.
In fact, for the so-called “antechamber” in Cheops pyramid, it isn't really possible to talk about a chamber, this space is actually nothing more than a fairly narrow passage. This "chamber" is to be seen as the timer mechanism to ensure that all automatic movements of the hydraulic system came in the correct chronological order. The antechamber is by far the most complex design of the entire pyramid.
We are told that this pyramid was built by a people who were still at the beginning of a great civilization, yet it’s impossible to fully understand the operation of this extremely ingenious mechanism. In reality, the operation of the "antechamber" is far too complex, therefore it's still not possible to find a correct and complete explanation. There’re still many details in this construction that still can't be explained.
So, the following hypothesis regarding this mechanism will be only a partial explanation of it, and may be completely wrong!
Ante 01 – Part of the kings chamber with the entrance.
Ante 02 – Cad drawing by Rudolf Gantenbrink 
Thickness of the walls of the kings chamber,
3,29 cubit (3+2/7 cubit) = 172 cm = 67,7 inch.
Ante 03 – Picture by Jon Bodsworth.  – looking south
Thickness of the walls at the entrance of the kings chamber,
3,36 cubit (3+2,5/7 cubit) = 175,8 cm = 69,2 inch.
The walls of the kings chamber have a thickness of 3.29 cubit (3+2/7 cubit). According Petrie, at the entrance these walls seems to be a little thicker, namely 3.36 cubit (3+2.5/7 cubit). It may have been the intension to make the passage from the antechamber to the kings chamber exact 2 by 2 cubit. However, the granite floor blocks of the kings chamber, the two granite floor pieces in the antechamber and the large limestone threshold at the end of the great gallery (the entrance to the antechamber) aren’t lying in one plane, all these floor pieces are lying on a different level (height). The height of the passage to the kings chamber isn’t exact 2 cubit , but 2.1 cubit instead (according Petrie). 
On the picture above, we can see the thickness of the wall of the kings chamber (3.36 cubit) and one granite floor piece of the antechamber (4.21 cubit). Both granite floorboards fit very closely together. Some pieces of the floor have visibly broken off, perhaps due to the great tension on the connection between the two. As we have already seen with other constructions (e.g. the Osirion in Abydos), it can be expected that both parts will be very firmly attached to each other by means of dovetail joints, but in such a way they still could shift relative (vertically) relative to each other.
Ante 04 – The measures of the walls and the entrance
of the kings chamber, the height is now 11.15 cubit.
(Height originally intended to be 11.18 cubit?)
Ante 05 – The antechamber in front of the passage to the kings chamber.
The so-called “antechamber" is located just in front of the entrance to the kings chamber. This chamber was built with limestone blocks, more correctly explained, this space was left open in the solid limestone core of the pyramid. The height is 7.24 cubit (379 cm or 149.2 inches), the width 3.14 cubit (164.4 cm or 64.7 inches) and the length 7.14 cubit (373.9 cm or 147.2 inches).
The South Wall, a large granite block.
Ante 06 – A large granite block in the antechamber,
just above the passage to the kings chamber.
In the antechamber, just above the entrance to the kings chamber, there is a large granite block with a height of 4.5 cubit, this granite block doesn't reach the ceiling, the open space above this granite block was (afterwards) filled with a block of limestone.
Ante 07 – The large granite block in the antechamber, just above the passage to the kings chamber. Above this granite block sits a limestone to close the gap between the granite slab and the ceiling of the antechamber.
Ante 08 – Picture by Jon Bodsworth.  – looking south
The large granite slab and the smaller limestone block above it
to close the gap between the granite slab and the ceiling of the antechamber.
It's generally assumed that above the entrance to the kings chamber there sits only one large granite monolith that is part of the walls of the king's chamber. This isn't correct, above the entrance there are indeed two separate parts. First, there are the granite blocks in the walls of the kings chamber. Second, there is the granite block in the antechamber, the block with those 4 vertical grooves in it.
Here again, it can be expected that both parts will be very firmly attached to each other by means of dovetail joints, but in such a way they still could shift relative to each other.
Ante 09 – Drawing by Maragioglio & Rinaldi  - ©
Maragioglio & Rinaldi have understood this very well, in the above drawing you can clearly see that granite block. The walls of the king's chamber and this granite block are drawn as two separate parts. In this drawing, the passage from the antechamber to the king's chamber has a length of 256 cm (179 + 77 cm), which equates to 4.9 cubit (100.8 inches).
According to Petrie, the total distance from the threshold in the great gallery to the floor of the king's chamber is exactly 16 cubit (approx. 330 inches or 838 cm). The drawing above shows a total of 839 cm (179 + 220 + 120 + 164 + 156 cm), so this drawing is very accurate and fits very closely with Petrie's data. Still, for both the walls of the king's chamber and the granite block in the antechamber, Maragioglio & Rinaldi specify a thickness of 128 cm (= 2.44 cubit = 2 + 3/7 cubit or 50.4 inches).
(See photo Ante 03) - Based on Petrie's measurements, we arrive at a thickness of 1.5 cubit for the granite block and 3.36 cubit for the thickness of the walls of the king's chamber. Together this also amounts to 4.86 cubit. So for the thickness of this granite block, there is quite a big difference between the two values. It is not known which of these two values would be the correct one.
For the hypothetical explanation regarding the usefulness of this granite block, the thickness of it is of minor importance. More important is the possibility that this granite block and the wall of the king's chamber are very tightly connected to each other, perhaps with dovetails, but in such a way they could still shift vertically relative to each other.
Ante 10 – Photo by the brothers John & Morton Edgar – 1910, 1913. 
The south side of the Antechamber.
Original text: The south wall of the Ante-Chamber in the great pyramid of Gizeh, showing the four deep grooves which divide the wall into five equal spaces; Also the low passage which leads southward to the king’s chamber.
The photo above shows that a large part of the front block has broken off. Behind it one can see a straight part where nothing has broken off. This makes it clear that there is second block behind the first one, this is a granite block from the wall in the king's chamber.
Ante 11 – Photo by the Edgar brothers (1910-1913). 
The south side of the Antechamber.
Behind the granite block with the four grooves there’s a piece visible of another block behind it (yellow), this must be a part of the wall in the kings chamber. Has that block in front a thickness of 1.5 cubit or is it a lot thicker?
Ante 03 – Picture by Jon Bodsworth.  – looking south
Not so long ago, this granite block was very neatly repaired.
Although this granite block has been very neatly repaired, it is not an exact restoration. Originally, these four grooves did not extend all the way down, but ended a short distance from the bottom. Since everything, even the smallest details, had a specific purpose in the pyramid, we also have to consider this small detail.
Petrie : [start quote] The south wall has four vertical grooves all up it, which have been hitherto supposed to have extended down to the top of the passage to the King's Chamber. This was not the case, however; for, though much broken away, it is still clear that they became shallower as they neared the bottom, and probably [p. 78] ended leaving an unbroken flat surface over the doorway. [end quote] - [Flat surface roughly 5 inch?]
Ante 12 – Drawing by Maragioglio & Rinaldi  - ©
Yes indeed, the drawing by Maragioglio & Rinaldi is very accurate and this detail can be seen very clearly. What they didn't draw is the piece of limestone on top of the granite block to close the gap between this block and the ceiling of the antechamber.
Ante 13 – Drawing by Maragioglio & Rinaldi  - ©
Ante 14 - The cross section AB shows what these grooves must have looked like.
Those four grooves are still clearly present. They gradually become shallower and eventually stop completely, leaving a small flat surface on the bottom of the granite block. These grooves must have had a definite purpose, surely they weren't there for decoration. However, no explanation has yet been found for what the real purpose has been.
The east and west wall.
Ante 15A – In front of the east wall of the antechamber a large granite slab was mounted. The height of this lab is 5 cubit and the top side is flat.
Ante 15B – The granite block (south wall) is resting on this large granite slab.
Ante 16 – Picture by Jon Bodsworth.  – Looking south
The granite block (south) and the large granite slab
against the east wall of the antechamber (left).
The height of this granite slab is 5 cubit and has a flat topside.
Ante 17A – In front of the west wall of the antechamber another large granite slab was mounted. The height of this slab is 5.5 cubit and the topside has semicircular recesses.
Ante 17B – On the west side of the antechamber,
the granite block is also resting on a large granite slab.
Ante 18 – Picture by Jon Bodsworth.  – Now looking North.
The large granite slab against the west wall of the antechamber (left). The height of this granite slab is 5,5 cubit and the topside has semicircular recesses. Also on this photo (right side) the so called "granite trap door" (2 pieces) which is still hanging in its grooves. These grooves doesn't reach the floor but stop approx. 2 cubit above it.
Ante 19 – Picture by Jon Bodsworth.  – Looking South.
The granite block on the south wall of the antechamber is supported by the large granite slabs on the east wall (left) and the west wall (right) of the antechamber.
Ante 20 – The complete granite structure inside the antechamber.
Ante 21 – The antechamber in front of the passage to the kings chamber.
Ante 22 – The floor of the antechamber.
On the drawing above: The limestone threshold, sitting in the great gallery just in front of the south wall, which is in total 6.14 cubit long, 3 cubit in the great gallery and 3.14 cubit in the passage towards the antechamber. In the antechamber itself there are two granite floor blocks resp. 2.29 and 4.21 cubit long. Further on there's the passage from the antechamber towards the kings chamber which is 3.36 cubit long, in fact this is nothing more than the wall thickness of the kings chamber. The total length is exact 16 cubit, this with the threshold in the great gallery included.
Ante 23 – Three pairs of gutters.
On the drawing above: Three pairs of gutters, the first pair in the limestone threshold, the second in the granite floor block of 2.29 cubits and the third in the floor block of 4.21 cubits. Nowadays, these gutters are closed, in fact, they only seem to be just recesses in those floor blocks. Have these ever been real, open channels?
Ante 24 – The granite leaf, still in situ.
A granite leaf, consisting of 2 pieces standing one above the other, is resting in these "half" grooves. On the north side, a piece of the top blade has not been chopped off, this looks somewhat like a kind of handle.
Ante 25 – Picture by Jon Bodsworth. .
The “handle” on north side of the granite leaf.
This is a picture of the “handle” on the north side of the upper part of the granite leaf. Some called it a handle, Petrie on the other hand called it a patch or boss.
Petrie  : [start quote] This leaf is not simply a flat slab of granite, but on both its upper and lower parts it has a projection on its N. side, about 1 inch thick, where it is included in the side grooves. The edge of this projection down the W. side has been marked out by a saw cut; and the whole of the granite on the inner side of this cut has been dressed away all over the face of the leaf, leaving only one patch or boss of the original surface of the block [end quote]
Ante 26 – Picture by Jon Bodsworth. .
The granite leaf, view of the south side.
Here are two little holes in it of about 14 cm deep (5.5 inch).
Tadema  [start quote] : The two-part trap door still in situ has never been able to descend. The top part of this trap door is roughly rounded along the top edge and has a handle on the north side. The south side of the stones, in the bottom center of the top stone and at the top of the bottom stone, have two fairly deep holes about 14 cm deep. [end quote]
In the massive part of the pyramid, a space was left open for the antechamber. At first, the granite block on the south side was mounted in that open space and pushed up with struts. It's possible this granite block came all the way to the ceiling (without the extra piece of limestone now on top of it). Probably afterwards the granite slabs were placed on the east and west sides upon which the granite block from the south side could be lowered. The ceiling of the antechamber was presumably already present when the granite leaf (the so-called trap door) had to be installed. If this granite leaf, which still rests in these half grooves, was consisting of one single block, it would have been higher than the space between these grooves and the ceiling of the antechamber. So, this granite leaf couldn’t be made in one piece for the simple reason that such a large block couldn't be slid into the grooves. So, for this reason this granite leaf was made of two parts. Yet the “handle” and the two rather deep holes suggest that once both parts were firmly connected to each other. In fact, it is possible that both parts were once clad with one large plate (lead, red copper, bronze?) which was placed over the rounded top and completely covered the recess on both the north and south sides.
References to chapter I
 – Rudolf Gantenbrink
See his website www.cheops.org
 – Photos taken by Jon Bodsworth.
Jon’s own photos of the pyramids and surroundings.
 – Drawing(s) by Maragioglio & Rinaldi.
L'Architettura della Piramide Menefite, Rapallo 1965, Vol. IV
PDF Drawings Online:
 - Drawing by the Edgar Brothers.
Great Pyramid Passages, Volume 1 & 2 , (1910 & 1913)
John Edgar & Morton Edgar.
Photos public Domain, see Wikimedia:
 – W.M. Flinders Petrie – The Pyramids and Temples of Gizeh – 1883.
Book online: http://www.ronaldbirdsall.com/gizeh/index.htm
 - Auke A. Tadema.
De Piramiden van Egypte (Dutch) book by Bob Tadema Sporry & Auke A. Tadema
ISBN 90 228 3315 1 – 1971 -1977 – 1980