Is mattress stitch the same as flat seam assembly? I am about to assemble a child’s sweater… where garter stitch has been used decoratively along the shoulder seam with the sleeves. It calls for flat seam assembly… just not sure if that is the same as mattress stitch.

Flat seaming is a way of weaving two pieces together that is similar to mattress st but not exactly the same. There’s a diagram and short discussion toward the bottom of this web page.

That was helpful… thank you!