Flat-Felled Seam

A flat-felled seam takes two fabric panels, folds one seam allowance over the raw edges of both, and stitches the whole assembly down with two parallel rows of visible topstitching, the same construction running up the inseam of a pair of jeans. Every raw edge ends up enclosed inside the fold, so there's nothing exposed left to fray, which is why this seam shows up on garments built to survive repeated hard wear.

You'll find flat-felled seams on Carhartt and Dickies work shirts, denim jackets, and heavy-duty coveralls, wherever a garment needs to hold together through jobsite abuse and industrial laundering rather than gentle home washing. It's slower and more labor-intensive to sew than a standard seam, part of why it's reserved for workwear and denim rather than a basic cotton tee.

When sourcing work shirts or jackets for a bulk custom order, check the side and sleeve seams for flat-felled construction before committing; it's a fast visual signal that the garment was built for durability, not just appearance, and it holds up to the abrasion of tool belts and repeated flexing far better than a single-stitched seam.

Buyers sometimes assume any seam with visible double stitching is flat-felled, but plain double-needle hemming shows two rows of stitching without folding and enclosing the raw edge underneath. True flat-felled construction has zero raw edge exposed inside the seam, and you can confirm it by checking that the fold is fully sewn shut.