What essential technique is used to establish even length during a haircut?

The essential technique used to establish even length during a haircut is the guideline. A guideline serves as a baseline for the haircut, helping the barber ensure that all subsequent hair sections are cut to the same length. By establishing a clear and defined guideline at the beginning of the haircut, the barber can maintain consistency and achieve a balanced look throughout the entire style. This technique is crucial for creating precise shapes and styles, as it dictates how the rest of the hair will be cut in relation to the initial length set by the guideline.

While other techniques like layering, point cutting, and slicing are important for adding texture or blending, they rely on an initial guideline to achieve overall hair length uniformity. Without a guideline, it would be challenging to ensure that the haircut maintains an even length, leading to an unbalanced or uneven hairstyle.