After Sa'i, men should get their heads completely shaved (Halq) or get their hair clipped (Qasr) to the length of the upper third of their finger or a little more. Both shaving and clipping are permissible for men, though shaving is Sunnah & preferable. Women are, however, allowed to have a lock of their hair clipped. They are forbidden to shave their heads.
The fuqaha’ are unanimously agreed that shaving the entire head is preferable to cutting the hair, because it is proven that the Messenger of Allaah (peace and blessings of Allaah be upon him) shaved his entire head, and he prayed for those who shaved their heads three times, and for those who cut their hair once.