The detachable thumb is a close-up illusion in which the performer appears to remove a section of their own thumb. Its originator is unknown.
Effect The performer appears to remove the end of their own thumb; moving it back and forth along their hand or lifting it up.
Method There is no particular secret to this illusion: the performer simply holds out one hand sideways with the palm out and the tip of the thumb folded down behind the hand. Then, they place their other thumb bent so that the tip appears to be connected to the folded-down thumb with the forefinger bent to cover the joint.YouTube video showing how this trick is done
See also Thumb tip
References