If the shoe fits
Before the advent of the X-ray machine in the early 1900s, doctors could often only guess if someone had a broken bone, not to mention the location of the break. Feet are full of bones, so some entrepreneur decided X-rays should be used to measure them. This gadget was sold to shoe stores so salespeople could take a precise measurement before fetching the exact size from the stockroom. Customers would insert their feet in a slot (not pictured) on the platform on the other side of the machine.