Thickness measuring instruments are tools that are used to measure the thickness of an object. These instruments can have different shapes and sizes depending on what they are to be used for. An example of a thickness measuring instrument is a caliper with depth gauge that is used to measure the thickness of materials such as paper, cardboard, or plastic. Another example is a micrometer, which is used for very accurate measurements of thin materials such as metal foils or glass plates. There are also specialized thickness measuring instruments for specific applications, such as ultrasonic thickness gauges for measuring the thickness of pipes or coatings on surfaces. As a rule, thickness measuring instruments are used in industry, crafts and research to make accurate measurements of materials and products.