Hazrat Saeed bin Jubair used to tell those shaving the head to bring the shave up to both bones.

Hazrat Ibn Umar (may Allah be pleased with them both) used to say to those who shave (their heads) that when performing Hajj or Umrah, shave up to both bones.

Ibn Abbas (may Allah be pleased with them) used to instruct those shaving their heads to start shaving from the right side and to shave up to both bones.

Hazrat Ali (may Allah be pleased with him) Al-Azdi narrates that Hazrat Ibn Umar (may Allah be pleased with them both) performed the sacrifice and had his head shaved. I heard him saying to those shaving heads, "Shave up to the two bones." Hazrat Ibn Jurayj says that I asked Hazrat Ata, "Did you yourself hear him saying this to those shaving heads?" He replied, "I have heard people mentioning this, but I have not heard it from him myself."

15188 - He said: (So I said to Ata: Did you hear him say regarding shaving: "Up to the two bones"? He said (1): I heard them mention it, but I did not hear it from (Thabit) (2).

Hazrat Abu Ja'far says: "Shave up to the bones."

Hazrat Ata says that the Sunnah method is that the shaving (of the head) should be up to both bones.