While it’s obvious that stitching is what holds your pair of selvedge jeans together, what’s not so obvious are the differences between all of these stitches. There’s a chain stitch, lock stitch, topstitch, whipstitch, overlock stitch, flat-felled seam…let’s just stop there. For this article, we’re going to focus on the qualities and differences of those last two: the overlocked vs. flat-felled seam.

First, let’s talk about overlock stitches. An overlock is a stitch that sews over the edge of one or two pieces of fabric for edging, hemming, or seaming. It has a recognizable appearance, and is often known as “serging.” Classified by the number of threads in each type, an overlock features threads that often loop under and over each other.

Overlock stitching is strong enough, but its winning factor is how efficient it is. There are industrial sewing machines that are designed to solely produce overlock stitches, and they run at very high speeds–anywhere from 1000 to 9000 rpm.

However, it’s important to not confuse efficiency with quality–as many selvedge denim fans can appreciate. Overlock stitches that come into frequent contact with the wearer (like say, a crotch prone to blowouts) end up not being as durable as one may think. Instead of stopping fraying from the outset, it merely slows it down due to the interwoven nature of its threads. Luckily, flat-felled seams exist.

At a base level, a flat-felled seam is an overlapping seam that’s sewn flat. Placing one edge inside a folded edge of fabric, the fold is then stitched down to create a flat surface. Extremely durable and sturdy, less threads are exposed to the wearer, leading to less fraying. Aside from that, flat-felled seams tend to look much cleaner and more appealing.

Of course, any particular brand has its own views on their stitching methods and the hours that go into them, so please take this simple guide with a grain of salt. Denim durability is a constant point of conversation, enough so that people now generally understand that they should wash their jeans if they want stitching to last. Either way, feel free to shop more confidently now that you have a few more stitching terms in your arsenal.