SETUP: Attach a rope to a cable pulley (a straight bar can also be used, but is harder on the elbows). Take a neutral-grip on the rope and turn around so you are facing away from the machine, arms now overhead.
REP: By keeping your elbows in tight with your arms overhead, your triceps will already be working in the stretch position. Now press the rope overhead and squeeze the life out of them.
TIP: The pulley should be set at around chest height, for most people this means they can twist in to and out of the move without having to get into an uncomfortable position.