Lego has a two-stud brick with a 45° slope that's used as a control panel on various vehicle kits, from automobiles to underwater craft to extraterrestrial shuttles. George Cave, a senior interaction technologist at KISKA in Salzburg Austria, collected 52 different Lego control panels and use them in a terrific mini-course in physical interface design.
Here's an excerpt:
Differentiating inputsRead the rest
What could cause 400 WWII pilots to raise the landing gear on their B-17 bomber just before touchdown? Catastrophic pilot error, or something more fundamental?
It was the psychologist Alphonsis Chapanis who first suggested that the high rate of crash landings might be the fault of poor interface design. The adjacent landing gear and flap control knobs were identically shaped. The pilots never stood a chance.B-17 belly landing, and the shape coding that helped to irradiate the problem. Source: Wikipedia
His temporary solution was to glue differently shaped strips of rubber to each switch, enabling blind operation by touch alone. This gave rise to the idea of shape coding and a system of differentiation still being followed in aircraft cockpits today.
We can compare the three interfaces [at the top] to see this in action. Ignore the overall layout, it’s the differences between individual switches that matter here. Imagine trying to feel for one of these buttons without looking. The left panel (“Slope 45 2 x 2 with 12 Buttons”) would require careful hand-eye co-ordination. The right panel (“Aircraft Multiple Flight Controls”) clearly distinguishes between the throttle (large, linear vertical movement), toggle switches (round vertical flick) and the push buttons (square push-in).