Breaking Perimeters

Cutting hair with thinning scissors
Photo: Maksvil/Shutterstock
Q: I saw a pair of thinning scissors on Sharpline Scissors' website - they had 16 teeth! It said they were great for "breaking perimeters". What does that mean?
A: The term breaking perimeters refers to softening the weight line in a haircut.
Allow me to explain briefly for those who may not be familiar with the terms. The "perimeter" of a haircut is the outline created by the ends of the hair around the head. In a basic blunt haircut, the perimeter follows the ends of the hair around the head. This is also known as a "weight line" because it is where the hair appears thickest.
Many hairstyles have weight lines in various places, some of which are desirable, some of which aren't. Using these types of thinning shears - with widely spaced teeth - you can break the prominent appearance of these "perimeters" or "weight lines" because the shears remove a percentage of the hair below the point the shears are used.
The overall effect is that the clean, solid perimeters (weight lines, cutting lines, etc.) are softened, and the hairstyle takes on a smoother look.
See also:
Hairstyling terms and definitions
What is a good number of teeth in one sided thinning shears?
What is the purpose of thinning shears with double rows of teeth?
What do I need to know to buy the right thinning shears?