"To build the flying buttress, it was first necessary to construct temporary wooden frames which are called centering. The centering would support the weight of the stones and help maintain the shape of the arch until the mortar was dry. The centering was first built on the ground by the carpenters. Once that was done, they would be hoisted into place and fastened to the piers at the end of one buttress and at the other. These acted as temporary flying buttresses until the actual stone arch was complete."