A decade ago two San Francisco Bay Area architects Ronald Rael and Virginia San Fratello reflected on the trade and labor imbalances between the U.S. and Mexico and imagined an art installation that would serve as a thought-provoking metaphor for how actions on one side of the border had direct consequences on the other.  The discussion led them to create architectural drawings and models for a “Teeter-Totter Wall” interactive display.  The work drew the praise from both the Museum of Modern Art in New York and the San Francisco Museum of Modern Art, but the actual installation remained just a concept until this week.