The modifed ground pinky lock is a finger lock of the pinky executed from the ground position. It invloves stipping the pinky of your opponent's grabbing hand and bending it backwards and sideways to dislocate/break the joint or control your opponent via pain compliance.
STEP 1: Your opponent grabs your forearm/wrist with his same side hand.
STEP 2: Rotate your grabbed forearm. Push your elbow forward and up, move your wrist down and inward to expose your opponent's pinky.
STEP 3: Reach over with your opposite hand and peel/strip his pinky off your arm.
STEP 4: Rotate his pinky backwards, down and sideways in induce pain or dislocation of the finger joint. The rotation comes from the wrist extension of your opposite hand.
WATCH THE VIDEO
Due to the relative weakness of the pinky, your opponent will not be able to resist the finger lock. Although, he may be able enable his finger to escape it before the lock is fully engaged.