Answer:
The Ruler and Tape Measure
The ruler -- a flat length of wood or metal graduated in traditional English units, metric units or both -- is the most basic tool for measuring length. Typical rulers are either 1 foot or 1 yard in length. When you replace rigid wood or metal with either thin, flexible metal or fabric, you have a ruler that you can use to measure curved shapes. Make this ruler as long as you like and store it in a container and you have a tape measure, a tool no builder or tailor would be without.
Calipers and Opisometers
Technicians working in laboratories need more precision than tradespeople, and they use a vernier caliper to measure lengths as well as the inside and outside diameters of round openings. The caliper has a set of jaws that can fit over objects as well as inside openings, and you read the space between the jaws on an accurately graduated ruler. A micrometer is another type of caliper that relies on screw threads for accuracy. For measuring curved lines, mapmakers use an opisometer, a wheel connected to a calibrated scale. By running the wheel along the line, you can read the distance the wheel travels from the scale. The measuring wheel that landscapers use to measure long distances operates by the same principle.
Explanation:
