If you've ever been folding a stack of bath towels and wondered why they have lines near the edge, you're not alone. I was also curious, so I asked Emma Seymour, the associate director of the Textiles, Paper & Apparel Lab for GH US, what the real reason for those bath towel lines is. She told me that it's called a "dobby border" and explained why most (though not all) bath towels have them.

Many people assume the line on the towels is purely decorative, or that it's meant to make it easier to see that all your towels are folded and facing the same way when they're stacked in the linen cupboard. But according to Seymour, the lines on bath towels aren't merely decoration. They actually serve to make the towel more durable.

If you've got towels on the brain, you can also check out our collection of clever uses for old towels and find out how to keep your towels fluffy for longer.

Below, Seymour explains exactly why your bath towels have those lines.

What's the purpose of a towel line?

'It's the dobby border, common on many bath towels,' says Seymour. 'It helps the towel keep its shape because it offers more structure than if it was entirely terrycloth. It also helps prevent fraying.'

What is a dobby border?

A dobby border is a woven strip near a towel's ends. It can appear as a single strip or multiple, but it is always located near a towel's edges.

According to Seymour, 'Testers tend to like the look of the border, but most don't comment on it if a towel lacks a dobby border,' meaning it's not a make-or-break feature for most customers.

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Do towels need a dobby border?

Not necessarily. A towel without a dobby border will still absorb, as is its primary function. However, it may not have the same durability and longevity as one with a dobby border.

It's about weighing out what's most important to you when shopping. If the price is right, and you like the look of a towel without a dobby border, buy it. There are other factors that contribute to a towel's durability and performance, such as fibre content, fabric weight, construction and more, not just the dobby border. So the towel you select may still go the distance.