We CNC machined these odd-looking devices that were designed to be purely functional and dimensionally critical.  The actual sockets were made by different vendors abroad, and had to constrain to tight tolerances to fit just right.  The Bay Bridge engineers had the idea to build these check-fit devices to send to the manufacturer to ensure that every single suspender socket would conform correctly.  Their strategy worked and Caltrans engineers were spared the added cost of having to remake suspender sockets.