Final answer:
In a blunt, one-length haircut or when using over direction for length or weight increase, the guideline used is a stationary guideline. It provides a reference point that remains consistent throughout the haircut.
Step-by-step explanation:
The guideline used in a blunt, one-length haircut or used in over direction to create a length or weight increase is known as a stationary guideline.
This type of guideline is a fixed reference point that does not move during the haircut. It is typically established at the beginning of the haircut and used to ensure that all cuts are uniform in length.
When performing a one-length haircut, the hair is brought back to this guideline each time to ensure that the length is the same all over.
In over direction techniques, the stationary guideline helps create increased length or weight in a specific area, such as when creating a graduated or layered look.