The Relationship The detail is a structural 'arm' that holds panes of glass of the curtain wall as it curves around the front of the ship-shaped building. Each arm connects four panes of glass to the organic armature that wraps around the structure. The arm element is made from spheriodal carbon, which is stronger and easier to cast than steel in the complicated and organic forms of the building. Visualization Roll over the image to the left to visualize the transformation from reality to model form.