The foot was the original ruler and the thumb was the original inch. If you could take three of your feet and lay them end to end, they would reach from the tip of your nose to the end of your outstretched arm, or as we like to say nowadays, a yard. Since people's body parts are handy, it was convenient. But because they come in all different sizes, it lacked something in consistency from one craftsman to another. So rulers, yardsticks, tape measures and other tools were developed to create a standard that meant the same thing to everyone.