A pinnacle (from Latin pinnaculum, a little feather, pinna, compare panache) is an architectural ornament originally forming the cap or crown of a buttress or small turret, but afterwards used on parapets at the corners of towers and in many other situations. The pinnacle looks like a small spire. It was mainly used in Gothic architecture.
The pinnacle had two purposes:
# Ornamental - adding to the loftiness and verticity of the structure. They sometimes ended with statues, such as in Milan Cathedral.
# Structural - the pinnacles were very heavy and often rectified with lead, in order to enable the flying buttresses to contain the stress of the structure vaults and roof. This was done by adding compressive stress (a result of the pinnacle weight) to the thrust vector and thus shifting it downwards rather than sideway.