Yubi Tori
Yubi Tori is a Yawara technique in Danzan Ryu Jujitsu.
Technique Description
Uke (attacker) reaches for Tori. Tori grasps Uke's ring finger, folds the tip into Tori's palm, and applies force to the finger tip to either cause pain or break the finger.
Variations
Straight finger locks
Many variations involve bending Uke's fingers back towards to back of the hand.