Hairline Correction
A hairline is judged by the proportions of the whole face, not by how wide the forehead is.
Hairline correction transplants hair to adjust the balance between forehead and face. A broad forehead, an angular one, and left-right asymmetry each have different causes, so each is designed differently.
What matters is not where the line sits but how it behaves. A hard edge reads as artificial, so the leading edge is planted sparsely and density rises behind it. That gradient is what makes it look natural.