A method which is often advertised is the penis pump. This is a cylinder that is fitted over the penis, with a manual or motorized pump to create suction. As the apparatus creates a vacuum around the penis, blood is drawn into the penis causing it to become engorged.
The higher the vacuum, the higher the blood-pressure becomes within the penis; excessive pressure causes vascular damage rather than a harder penis.
Over-enthusiastic pumping can burst blood vessels and form blisters. In some cases the testicles can be unexpectedly pulled into the cylinder and cause severe pain and injury. It is also believed that the rim of the cylinder can cut into the skin and over time cause damage to the ligaments surrounding the penis. Impatiently pumping can produce to much suction (anything over 10 mm Hg) and cause permanent injury.
Attempts at using vacuum cleaners units for this purpose have resulted in severe injury as the machine produces far too much suction. If the base unit is used without a hose there is also the danger of coming into contact with the rapidly-rotating fan.
Penis pumps are also used for masturbation. For example, in August 2006, Oklahoma district court judge Donald Thompson was sentenced to four years in prison for repeatedly having masturbated with a penis pump while presiding over court cases.
The idea behind vacuum pumping is that you will force blood into your penis and force it to grow. Now, this may sound erotic or reasonable, but beware, a vacuum pump can injure your penis easier than it can permanently enlarge your penis, simply because it’s forced vacuum power, not gentle stimulation exercise.