Machinery onboard ships require regular care and maintenance so that their working life and efficiency can be increased, and the cost of operation, which includes unnecessary breakdowns and spares, can be reduced. For different types of machinery and systems, various measuring tools, instruments and gauges are used on a ship. Measuring instruments and gauges are used to measure various parameters such as clearance, diameter, depth, ovality, trueness, etc. These are critical engineering parameters, which describe the condition of the working machinery. Below, we have compiled a list of mechanical measuring instruments and mechanical gauges which are extensively used on the ship for the recording of different parameters. There are many instruments, tools and gauges which are used on a daily basis onboard ship for measurement, fault finding, wear down etc.