You can also use a low pulley and pull upward from a standing or seated position with a rope or straight bar. Some gyms have machines that come very close to duplicating this movement. This movement is one of the most popular for working the triceps. If you feel uncomfortable with the weight being lowered to your head, try lowering it just above your head. As you become more familiar with the movement, concentrate on lowering it to your head.
Some lifters say they get a fuller pump by lowering the bar above their head.
This is a great movement to finish with. It really burns the triceps, and if you pause slightly at the top of the movement as you lock out your triceps, you will really feel it. These can be done as pictured or bent over leaning against something sturdy. Position the dumbbells straight back one workout and slightly outward on the following workout. By leaning forward from a standing position you can do both arms at the same time and use heavier weight.