Which specific area of the coat is prone to painful matting due to friction against the dense undercoat?

Answer

Behind the ears, in the armpits, and around the collar line

The dense, soft undercoat is prone to creating mats in areas of high friction, specifically naming behind the ears, in the armpits, and around the collar line.

Which specific area of the coat is prone to painful matting due to friction against the dense undercoat?
DogbreedcoatSlovak Cuvac