What is a feeler gauge used for?

• A. Used for setting air gaps on various objects such as spark plugs.
• B. Used for cutting nails.
• C. Used to mark metal with a scriber.
• D. Used to measure circumference.

Answer: (A)

Feeler gauges are used to measure small clearances. They consist of thin metal blades of precise thickness that you slide into the gap between two parts to check how wide it is. The idea is to find a blade that fits with a light drag; the blade’s thickness then tells you the gap size. In practice, this is how you set spark plug gaps and other small clearances in engines—you compare the gap to the specified thickness and adjust as needed to hit the exact dimension. It’s not a cutting tool, it doesn’t mark metal, and it isn’t used for measuring circumference, so those options don’t fit.