I began by hauling my Bernina down from the attic. I don't have a computerized sewing machine. I have the most basic Bernina. It sews backwards and forwards and zigzags when I want to get fancy. I bought it at a floor model sale at G-Street Fabrics in Rockville, Maryland years ago for the express purpose of having something decent to use for sewing open sweaters. I'd been spending more time unjamming my old Singer than sewing, so I wanted something better. My Bernina may not be a top-of-the-line model, but the little motor purrs and it does what I want it to.
I set it for small stitches (less than 2 on the dial) and sewed right down the centre of each of the two steek stitches on the front, being careful to anchor the top and bottom edges with some back and forth sewing.
Even though the steeks were sewn, I was careful to handle everything gently while I joined the shoulders with a 3-needle bind-off.
Next, I cast on 3 sts using the longtail method and dpns 2 sizes smaller than the body. I chose to use the darkest burgundy (contrast colour) for the I-cord border.
Notice that the working (long) end of the wool is at the rear of the needle. Next, I slipped the left-hand end of the dpn into the half of the border stitch (the outermost steek stitch) closest to the body. You'll see that I was working from the wrong side of the waistcoat, starting at the bottom of the left front. Remember, when working I-cord in a contrast colour, work from the wrong side to avoid colour blips showing through. (Remind me to have a manicure next time before taking closeups of my hands!)
Then, I took the wool across the back of the needle and knitted the first stitch on the needle, pulling the stitch snug. I knitted the second stitch, then knitted the last burgundy stitch together with the blue border stitch THROUGH THE BACK LOOPS.
The I-cord border and the waistcoat are married! Then, I simply slipped the left-hand end of the dpn into the next border stitch, as before, and repeated the entire procedure.
As I worked, the steek folded itself naturally to the inside, creating a useful facing. In case you're wondering, that's why I chose to knit a wide steek (8 stitches).
So tidy! See here for instructions for finishing the cut edges.