Which tool is essential for achieving different hair lengths in a haircut?

Shears are essential for achieving different hair lengths in a haircut because they are specifically designed for cutting hair. They allow a stylist to remove hair in varying lengths and create precise lines or blended layers based on the desired style. Shears can be used to slice through the hair for a straight cut, or they can be employed at different angles to enhance texture and shape. The versatility of shears makes them a fundamental tool in hairstyling, enabling professionals to execute a wide range of haircutting techniques effectively.

While a comb is important for sectioning and managing hair during a cut, it does not actively change hair length. A straightener is primarily used for smoothing and straightening hair, not for cutting. A razor can be used for texturizing and creating softer edges, but it is not the primary tool for determining and achieving different lengths in haircuts, as shears are designed to do.