re: Designing things so they can only be installed correctly...
On my 1st job out of college at Raytheon Missile Systems I built an IC module test chassis. It had 120v and 5v connectors. Identical. So after weeks of working on the underside wire-wrap side, I got it assembled and working so I finally turned the chassis right side up and plugged it in. Left became right. Not good, especially for someone slightly dyslexic working over 65 Hrs/week.
A letter from the lab boss ordering different style connectors for different voltages ensued.