To trim hair sections, secure your connection and use your thumb instead of your index finger to hold the hair in place. The section the comb is on can then be moved away for trimming.
The provided reference suggests that using the thumb for securing the hair section being trimmed, rather than the index finger, is a key element of professional sectioning technique. This method allows for better control and visibility when trimming. This single instruction is the extent of the information available for hair section trimming in the provided reference.
