To cross one's fingers is a hand gesture commonly used to wish for luck. Occasionally it is Wishing for luck is gestured by pressing thumbs. The same gesture.
Dec 8, When people clasp their hands, almost all have a strong preference; either the right thumb is on top (R) or the left thumb is on top (L).
Jan 5, Just ask any traveler who's given a thumbs-up in Afghanistan. Or someone who's crossed their fingers in Vietnam or signaled "OK" in Brazil. All.