What category of items should be used as a guide for thickness measurement in gunning?

Using shot board height and depth gauges as a guide for thickness measurement in gunning is critical due to their specific design and purpose in monitoring the application of refractory materials. These gauges are purpose-built tools that provide an accurate and consistent reference for measuring the thickness of the applied refractory material.

When gunning refractories, maintaining the correct thickness is essential to ensure optimal thermal performance, structural integrity, and durability of the applied refractory lining. The shot board height and depth gauges help in achieving uniformity and precision during the application process.

While calibrated instruments, visible markers, and general measuring tools might seem useful, they may not offer the same level of accuracy or reliability for this specific task. Calibrated instruments can be more complex and not necessarily tailored for thickness measurement in a gunning application. Visible markers can be subjective and prone to human error, and while measuring tools have their merits, they could lack the specific calibration or design features suited to the unique demands of refractory gunning. Hence, shot board height and depth gauges are the optimal choice for this function.