The split arm piece that engages the top lever spindle inside the action. The other end of the yoke engages the rotary bolt.
Push the top lever open, the yoke transfers the motion to the bolt and rotates it to unlock the bbls.
The screw that passes through the yoke and the spindle itself is the one which is usually peened over on the threaded end to prevent it from backing out,, and probably from tightening up anymore too.
It has to leave the arms of the yoke with some clearance to move about the spindle as it rotates the bolt.
