How do you use gap tool?

How do you use gap tool?
Before you start, just be aware that there are many plugs that you can not adjust the gap on. If these are old plugs, don't try adjusting the gap to account for electrode wear; the metal may be brittle and the outer electrode may break off in your cylinder.
if neither of these apply to you, here is how you can check/adjust a spark plugs gap. Slide the tapered gauge into the electrode gap and rotate it until it just fills the gap, but don't force it, read your gap there. If you need to adjust, there is a hole in the tool you can use to bend the outer electrode into position, but do it slowly and carefully.
Many auto parts stores sell the plugs pre-gapped for your vehicle. If they don't and the plugs need to be adjusted, they'll probably help you gap them there.