This arch has 19 sides (3 rods long by 2 wide) and the supports are rectangular pyramids with base 4 bars long by 2 wide. The inner construction to support the edges alternates between truncated equilateral trianges (10 edges) and a Isosceles Trapezoid with basis angle of about 70.5° (9 edges). Each module subtends an angle of about 10.5° to the center, so all nineteen modules make an arch of nearly 200°.