Tank car contents may be measured by three methods: railroad scale weighing, metering, and liquid level measurement. This standard describes only the equipment for and the procedures of the liquid level method of measurement. When tank cars can be opened for manual measurements, gauge tapes and bobs may be used to measure the level of liquid contents. When tank cars cannot be opened for gauging contents, closed-system measurement equipment must be used for gauging. This standard describes gauging and temperature measurement equipment used in both open and closed measurement systems.