Rulers were first used by the Indus Valley Civilization before 1500 BCE. Made of ivory, the rulers found during excavation, reveal the incredible accuracy of decimal subdivisions on it. Excavations at Lothal (2400 BCE) have yielded one such ruler calibrated to about 1⁄16 inch (1.6 mm). The Mohenjo-Daro ruler is divided into units corresponding to 1.32 inches (33.5 mm), and these are marked out in decimal subdivisions with incredible accuracy, to within 0.005 inches (0.13 mm). Ancient bricks found throughout the region have dimensions that correspond to these units.
Anton Ullrich invented the first folding ruler, and the first flexible ruler was made in 1902. The ruler has come a long way since then. Rulers now come in different shapes, sizes and materials. Rulers that are used for office work are usually made of wood. Rulers can be made in various sizes. The usual size for a desk ruler is 30 cm. A longer ruler size is 45 cm. Desk rulers are often used for general-purpose tasks, including math & geometry and drawing. Some small rulers can fit in a pocket and carpenter rulers that can be folded in a zig-zag shape. The folding rule or carpenters’ rule is a wooden instrument consisting of multiple flat wooden sections connected at the ends that pivot allowing the ruler to be folded. They are usually used for construction and carpentry and are regarded as more accurate than a tape measure and easier to use for measuring inside edges.
For measuring larger distances yardsticks (1 yard) and meter sticks (1 meter) are in use, but today they have been increasingly replaced by tape measure and laser rangefinders. Yardsticks are straight thin pieces of wood or metal used to measure objects up to a yard. They usually are 36″ in length and may include imperial or metric measurements. Then there is the architect’s scale, a type of ruler that has measurements in several different scales. They are most often made of wood or plastic and are 3-sided with six different measurement scales. Architects scales are used for engineering and architectural drawing such as drafting blueprints to scale.
Today, rulers have advanced with technology. So much so, that rulers now come with inbuilt calculators, pocket knives and a digital display of the measured unit.
The Indus Valley Civilization made rulers from ivory.