A recent viral post has shed light on a question many have wondered about: What is that raised line running across bath towels?

Though jokingly dubbed a “face-to-butt separator” or a “racing stripe,” the feature has a far more practical purpose.

Known as a dobby border, it’s not merely decorative. Textile experts explain it helps towels retain their shape and withstand repeated laundering.

One of its main functions is reinforcement. The dobby border strengthens the towel’s edges, reducing fraying and wear over time.

It also prevents the ends from becoming too thick or bulky. This keeps the towel evenly shaped, easy to fold, and comfortable to use—all while preserving absorbency.

Additionally, the border offers a subtle space for design. Manufacturers can add texture, patterns, or logos here without compromising softness or function.

So next time you reach for a towel, take a closer look. That small dobby border is a thoughtful detail, helping your towel last longer and perform better.