As the layers of blocks were placed on top of each other and slid into place by the use of scaffolds and pry bars, the blocks were then cut away and dove-tailed or pi-clamped "key" Fig 6-7 was used to keep them in place to limit separation.
As the block sides of the monument progressed, the formation of the arch could now begin. The builders would at this time structurally support the sides and top with framework as shown in Fig 8 to keep the arch from collapsing until the keystone blocks could be set into place. The keystone block Fig 9 was an integral component in arch construction as it joins the two sides of the arch together as the forces of the two sides press in towards each other. The stones for the arch were precision cut geometrically to fit together. The construction of the arch had considerable load bearing capabilities which is the reason it so popular became such an important part of the empires decorative and most importantly, its functional use's. As shown in Fig 9 each of the counter-key stones are pressing together equally on both sides while at the same time pushing apart.
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