This is not a major mass builder or strength developer but it a great movement for adding Volume to your tricep training. Why does this matter? For most, increasing work capacity is a HUGE factor when it comes to strength and growth BUT when using movements that are harder on the CNS (example: close grip bench presses) this can't be accomplished without over-training.
The solution is to use lighter less intensive movements as the first step and then move to the harder intense movements later.
This movement is performed just as it looks. Grab and bench, lay down and grab the cable. Start in a full extended position with your triceps flex and locked. Focus on bending the elbow first (not the hand) and lower to a full strength position. Many times if you focus on the hand you will have too much shoulder rotation (This is okay but is a whole other movement).
High reps (10-15) will work best with this movement.