Set a cable pulley as high up on the machine as you can and grab right onto the end of it without using any attachments at all.
Take 4-5 steps back and hold the cable with your elbow pinned at your side. Flex your shoulder joint by moving your shoulder and upper arm back a few inches behind your body.
Press the weight down and behind your body until your elbow is fully locked out. Pause momentarily before return back to the starting position.