Balance and contrast
The stylists' rule of thumb that a frame, beard or brow can either balance a face shape or echo it.
Also: opposites rule
Most face-shape advice rests on one idea. To balance a shape, choose the opposite: round frames for an angular face, angular frames for a round one, fullness at the chin for a narrow jaw. To echo a shape, choose a match, which strengthens it. Neither is correct. The rule is a starting point used by opticians, barbers and makeup artists, and many people ignore it to good effect. What a person likes wearing matters more than any chart.