During the course of the eleventh and twelfth centuries, walls became
higher and thicker, often sloping out at the bottom to counter attacks
with battering rams. The parapet on the outer side of the walk along the
top of the wall was notched with crenellations—that is, crenels (low
walls) alternating with merlons (higher walls), behind which men on the
wall-walk could seek protection (see the crenellated wall-walk at Aigues
Mortes, Figure 22). The merlons could be pierced with arrow loops, holes
through which archers could shoot while still being protected by the merlon.
Such walls did not permit adequate observation or defense of the
entire wall, because the men could not see the bottom of the wall without
leaning over the crenels and exposing themselves to the enemy’s
death-dealing arrows and rocks. The addition of towers built out in front
of the wall and galleries over the top of the wall solved this problem. The
wall-walk could be developed into a full-scale fighting gallery. Temporary
wooden galleries, known as hoardings, doubled or tripled the space available
for the defenders at the top of the wall (see Figure 12). Beams or
brackets supported the hoardings and permitted holes in the floor through
which the defenders could observe the wall and its base, shoot their arrows,
or drop stones and other missiles. Brief forays (sallies) outside the
walls helped to keep up the defenders’ morale.