They link pinky fingers. Then one went to touch thumbs and the other one went to bite her thumb. The end result was his thumb on her nose.
Giggling "what are you doing?"
"Apparently petting your nose," he starts to move his thumb in a circular motion on the tip of her nose, "what were you trying to do?"
"Bite my thumb to finish the pinky promise."
"I've never heard of that. I touch thumbs."
"To complete the promise and it's supposed to symbolize an unbreakable vow since circles are typically harder to break. Why would you bite your thumb?"
"That's the way I was taught." She thinks a bit further causing her to cock her head to the left and furrow her brow slightly, "I guess it means I would rather eat my own thumb than break my promise to you." she turns red as the blood rushes to her cheeks, and she giggles nervously.
"You would really rather eat your own thumbs than break this promise?"
"I would rather eat my thumbs than break any promise to you."