Which tool is specifically used to measure the width of a narrow slot?

The feeler gauge is specifically designed to measure the gap or width of narrow slots, ensuring accurate readings in tight spaces. This tool is made up of several thin metal strips of varying thicknesses, allowing it to fit into narrow openings. When measuring, you can choose the appropriate thickness of the feeler gauge to determine the size of the slot.

While other tools like calipers, micrometers, and screw gauges are versatile and can measure various dimensions, they are not specialized for working within tight spaces like a feeler gauge. Calipers have a broader measuring range and can handle larger objects, while micrometers and screw gauges excel at measuring small dimensions with high precision but lack the flexible design necessary for narrow slots. Thus, the feeler gauge is the most appropriate and specialized tool for this specific measuring task.