To ensure the chain sits perfectly flat without flaring or pulling the V-neck out of shape, drop down 1 or 2 needle sizes from your project's main needle size (e.g., if you knit the body on 4.5mm needles, use 3.75mm or 4.0mm circulars for this trim).
By binding off the stitches
the exact moment after they are pulled through the garment edge, you prevent any vertical fabric row from building up. The stitches are anatomically forced to tip over onto their sides. The result is a continuous, raised horizontal chain that locks down raw edges and mimics a crochet hook trail, achieved with pure, master-level knitting tension. [
1]