Building churches wasn't based upon a theoretical knowledge. Many constructions collapsed. Travelling teams of stone workers and wood carvers builded their knowlegde just out of experience. Little by little out of a shared knowledge one learned the do's and dont's in construction. [br]The builders, who were familiar with circular arcs and barrel vaults, gradually shifted from using circular arcs and barrel vaults to the use of pointed arcs and pointed barrel vaults.[br][b]Drag the green point out of the center and create a pointed barrel vault.[/b]

The abbey church of Fontenay (early 12th century) is a nice example of a pointed barrel vault. Side aisles with crosswise placed barrel vaults give extra support to the walls..