A simple question recently ignited a lively debate online: why do bath towels have that odd raised line across them? What seemed like a minor design detail quickly went viral, echoing past internet obsessions and turning everyday towels into a topic of real curiosity.

The renewed interest began after a post on X showed a towel with the caption, “What’s this line for?” The image spread fast, drawing jokes and guesses from users who wondered if it was decorative, functional, or something else entirely.

Some answers were purely humorous, including claims that it was “that’s the face-to-butt separation line” or even “racing stripes” to help towels dry faster. Others guessed it helped with folding or was simply a stylistic choice by designers.

Experts soon offered a clear explanation. The line is called a dobby border — a tightly woven strip found at the ends of most towels. Its main purpose is practical: it strengthens the towel, prevents fraying, and reduces bulk at the edges so the towel stays soft, absorbent, and durable after many washes.

As Towel Hub explains, “Absorbency is one of the most important qualities of a good towel, but achieving the perfect balance between thickness and performance can be challenging. The dobby border helps maintain structure and improve overall function without compromising softness.” It also helps towels fold neatly and look polished, proving that the line is more than just decoration.