Part of the penis is hidden under the pubic bone. To lengthen the penis the suspensory ligament that supports the penis is cut. Part of the penile shaft that is hidden drops forward and extends out.
It makes the penis look somewhat longer when it is flaccid, adding one to one and a half inch. But it only stays this way through continual stretching of the penis after the operation (by wearing weights), thus keeping it from retreating back.
There is not much gain in erect length. According to one study involving 58 men the average gain in erect penis length was less than half an inch. About 68% was dissatisfied with the results and 50% would not have surgery if given the chance to decide again.
In some cases cutting the ligament causes a shortening of the penis due to scar formation.
The cutting of the suspensory ligament will lower the angle of erection. It will point downward, aiming at the feet. It also makes the penis less stable during intercourse and more susceptible to injury.
The whole procedure can be painful. Most physicians are very reluctant to use this technique because of the complications.