What is the classic barbering tool used to perform clean necklines?

The classic barbering tool used to perform clean necklines is the straight razor. This tool is traditionally associated with barbering and is renowned for its sharp edge, which allows for precise and clean lines when shaping the neckline. Barbers often use the straight razor to achieve a smooth finish along the nape of the neck and to define the haircut's boundaries, contributing to a polished look.

Additionally, the straight razor provides control and precision that can enhance a barber's ability to create distinct lines and shapes. When blended with skillful technique, it can create a more defined appearance that complements various hairstyles.

While clippers are useful for more general cutting and fading, they typically do not provide the same level of detail as a straight razor when it comes to finishing touches like necklines. Shears and scissors are primarily designed for cutting hair and are not optimal for achieving the sharp, crisp definition that the straight razor offers on edges. Thus, the straight razor stands out as the quintessential tool for this specific task in barbering.