In the later Middle Ages, hoarding evolved into stone machicolations. Sometimes machicolations were used symbolically to recreate a castellated effect on unfortified structures. The keep , great tower, or donjon was a self-sufficient, last resort, place of refuge used during a siege. Most keeps were square or rectangular in shape, although there were round keeps. Some keeps were over 80 feet high and had walls over 17 feet thick.
Merlons are the solid parts of a crenellated parapet.
They were sometimes pierced with arrow slits. The builders would put a dam on the outlet side of the water supply, and control the water level in the moat. Some moats had stone casings, but most were left with earthen banks. Most castles, however, had dry moats, known simply as ditches. The purpose of water defenses was to prevent the castle from being besieged.