How clipper-over-comb works, when barbers use it versus freehand clipping or scissors, the correct comb angle and clipper speed for clean results, and the situations where this technique is the only option.
The classification system barbers use for hair texture and curl pattern, how different hair types respond differently to the same cutting technique, and the adjustments that produce better results on each type.
Why thick dense hair requires different technique than average-density hair, the specific adjustments barbers make to fades, bulk reduction, and texture work when cutting clients with heavy hair.
The specific technique for fading the temple area, how the curved hairline at the temple differs from the flat sides and requires a different clipper approach, and the mistakes that produce uneven or choppy results in this section.