Well, not sure stitch is the technical term, just what I use.... I start with a tack about every two inches along the seam, let everything cool on it's own, then add another tack and keep going in that manner til the seam is filled completely. If you work at it, get the voltage and wire speed set correctly, doesn't take much to finish the seam off other then a bit of grinding and sanding... Best part is, once the seam is filled it's never again going to serve as a trash and moisture collector!!!! Big thing is getting all the trash, rust, and seam sealer out befor you start welding. It's a long, slow process but when done correctly it won't cause any distortion or warping of the skin.....