Architecture Puzzler #108

Abacus, echinus, astragal, apophyge, and torus are all related to each other in what way?

The "switchable" privacy glass system description that follows is missing a key element. What must be added to make this system work? Two layers of polyester film coated with transparent conductive material and a layer containing liquid crystal sandwiched in between. The film is positioned between two layers of glass.