Unfinished walls reveal that Inca stonemasons left the top face of every new
course uncut until it was ready to receive the next course. First, masons cut the
bottom and lateral faces of the block of the new course. A matching bedding
joint to receive the already cut block was then carved out of the top of the course
already in place. A similar approach was used for the rising joints; it is the side
of the block already in situ that was carved to match the precut shape of its new
neighbor. The technique is one of trial and error. By trying the fit time and again
the masons obtained a perfect match.
A dismantled wall at Ollantaytambo shows the
exact imprint of the stones that have been
removed or fallen off. The imprint determines
the unique shape and position of the stone
that once occupied it. Jean-Pierre Protzen