Ruler

• This is the most basic of measuring devices and involves a scale being printed onto wood, plastic or metal. The ruler itself is accurately made to ensure the edges are straight and the scales accurate. In some cases, both metric and imperial measurements can be printed on to the same ruler. Rulers can be used in any number of situations, but are only useful for measuring distances in larger scales, such as centimeters and inches. They can also be cumbersome to use as they are a ridged measuring tool.
  
  

Tape Measure

• Tape measures are most commonly used in the construction industry and combine the good elements of a ruler and eliminate its drawbacks. A metal tape is rolled around a spool inside a plastic case. This can be drawn out to any length you want, and has both imperial and metric measurements. The tape is normally several meters in length, but like the ruler is only really accurate over larger distances. It also features a metal hook on one end of the tape that can be attached to the end of an object, allowing the tape measure to be drawn out a long distance without the need for somebody to hold it in place. Tape measures can also be made out of a more flexible fabric, plastic compound. These are more commonly used in the fashion industry for measuring the dimensions of people, or lengths of cloth.
  
  

Vernier Caliper

• The precision engineered vernier caliper is a high-accuracy tool designed to measure small distances with pinpoint accuracy. It consists of a scaled handle, similar to the ruler and tape measure, but features two jaws. The jaw at one end, nearest the zero point on the scale, is fixed while the other can be adjusted by the operator. The adjustable jaw can be moved to fit around the thickness of an object so measurements can be taken. Vernier calipers also feature two prongs on each jaw that allow the user to measure the inside diameter of a pipe. Some of the more expensive calipers have a digital meter.
  
  

Micrometer

• The micrometer is the most accurate of the thickness measuring tools and is only used in precision engineering industries. It is accurate to within fractions of a millimeter, and only uses the metric scale. It works in a similar way to vernier calipers in that there is one fixed jaw while the other is adjusted by rotating the handle. There are two scales printed on the handle of the micrometer, one on the rotating base that gives the larger reading, and one on the barrel that measures in fractions of millimeters. Like the vernier calipers, the more expensive micrometers sometimes have a digital display to indicate the measurement.
  
  

Laser Measurers

• There are ranges of very expensive, but incredibly accurate measuring tools which use lasers instead of printed scales. These are quite similar in operation to the vernier caliper and micrometer, but can also be fixed in a location, for example, in a factory producing precision engineered machinery. These are incredibly expensive and are normally designed for one specific purpose.