Function of the Hairs of the Head and Beard of Arich Anpin.
A"A's Hairs and Beard are operational channels — the cosmic-anatomical structures through which A"A's mercy descends.
Op. 105 introduces the Beard doctrine that runs through the rest of the A"A unit. The Hairs of the Head and the Beard are not decoration; they are operational channels with specific cosmic-mercy functions.
The Beard descends from A"A's Face — from the operational region Op. 102 named. The Beard's thirteen hairs (or Tikkunim, repairs) carry the thirteen Conduits of Mercy — the operational mercy-channels through which A"A's complete Kindness reaches the rest of Atzilut.
The Hairs of the Head are upstream of the Beard. They carry mercy at a higher anatomical level; the Beard takes that mercy and distributes it operationally downward. Together, the Hairs and the Beard form the cosmic-anatomical apparatus by which A"A's interior mercy becomes operationally available at the deed-relevant level.