Knuckle Thrower

The knuckle thrower is part of the coupler assembly and serves to push the knuckle into the open position as the lock is raised by the lock lifter. When the lock is raised part way and then released, the thrower seat on the lock comes to rest on the tail of the thrower in a condition called "lock set". If the lock is raised

further, the leg of the lock will push against the thrower's lock seat leg causing the thrower to rotate about the trunion. The knuckle actuating leg then pushes the knuckle open.

 
See it in action: