The official I Declare Thumb War Squared Circle is used for all thumb wrestling matches sanctioned by the Thumb Wrestling Alliance (TWA). 
The bell that is a ring... the ring that is a bell.

"Pin-or-Pop" thumb wrestling

Why the “Pin-or-Pop” rule for thumb wrestling? Traditional (or “folk”) thumb wrestling is done with only a pinfall to count as a win. Often, stronger participants pull and twist their opponents during the contest, making it less about the thumb… so we needed to fix that. Using the pin-or-pop method for sanctioned TWA events, we can be certain that only the best thumb wrestlers in the world are recognized as champion!