Which idiom is it?
To thumb through something
Which idiom is it?
The rule of thumb
Which idiom is it?
To twiddle one's thumbs
Which idiom is it?
To stick out like a sore thumb
Which idiom is it?
To be under someone's thumb
Which idiom is it?
To be all thumbs
Which idiom is it?
To give two thumbs up
Which idiom is it?
To thumb one's nose at (someone/something)
Which idiom is it?
To give two thumbs down
Which idiom is it?
To have a green thumb