When I was a young industrial designer at the erstwhile Sun Microsystems (now owned by Oracle), I was working on the design of a large server. The product had modules that could be removed and replaced quickly by system administrators if something went wrong. We wanted to find the most intuitive design for the rotating latches on either side of each module. Since engineering was on a tight schedule and physical prototypes were months away from being ready, we elected to do “paper prototyping,” where we showed drawings to users of the modules with different latch designs.