A seam is the line where two pieces of fabric are stitched together. It is the basic building block of garment construction. Every shirt, dress, and pair of trousers is made of seams. Some are visible, like the topstitched seams on jeans. Others are hidden inside, like the seams that join a lining to a jacket. The quality of a garment often comes down to how its seams are made.

Types vary by purpose. The plain seam joins two pieces with a simple stitch. The French seam encloses the raw edges, making it neat on both sides. The flat-felled seam is strong and visible, common on denim. The welt seam is similar but pressed to one side. The overlock seam uses multiple threads to finish the edge and join the pieces in one step. Each type is chosen based on the fabric, the garment's use, and the desired finish.

Seam quality affects durability. A poorly sewn seam puckers, pulls, or splits. Seam allowance, the extra fabric beyond the stitch line, matters too. Too little, and the seam frays. Too much, and it adds bulk. Pressing is essential. A seam pressed open or to one side lies flat and looks professional. A seam left unpressed looks homemade. In tailoring, seams are often taped or reinforced for structure. The details are invisible to most wearers, but they determine how a garment fits and how long it lasts.

Common types

• Plain
• French
• Flat-felled
• Welt
• Overlock