Rulers have long been made of different materials and in a wide range of sizes. Some are wooden but mostly rulers are made of plastic. Desk rulers are used for three main purposes: to measure, to aid in drawing straight lines and as a straight guide for cutting and scoring with a blade. Practical rulers have distance markings along their edges. Measuring instruments similar in function to rulers are made portable by folding (carpenter's folding rule) or retracting into a coil (metal tape measure) when not in use. View the full range here.