The invention of the ruler dates back to ancient civilizations, such as the Greeks and Egyptians. Used to make measurements in a straight line, the first excavated rulers were often made from wood or ivory.
The first known rulers appeared to have markings that had similar meanings to our currently used imperial and metric systems. The modern 12-inch ruler used today was supposed to equal the length of a man's foot, while the width of a man's thumb was equal to 1 inch. The rulers we use today are often made from metal or plastic and can be bent to accommodate objects that are not completely straight.