This is an original pattern stitch I developed a number of years ago. I call it "Underline Stitch" for the line of strands it forms across the work. It's best worked in a singles yarn because plies detract from the cohesive look of the strands. Also, it biases wildly, so a natural yarn that blocks well is a must. My swatches here are worked in Lamb's Pride Worsted on US 8 (5 mm) needles.
Loosely cast on any number of stitches.
Preparation row (RS): K every st wrapping yarn twice.
Row 1 (WS): K every st dropping the second wrap.
Row 2: For every st, with the right needle, go under the head of the next stitch in the row below from the bottom (Figure 1), lift it onto the left needle so it forms an "X" with the next stitch (Figure 2), put the right needle into the back of the 2 loops (Figure 3), and knit them tog from this position wrapping the needle twice.
To finish, work Row 2 with single wraps. Bind off on WS, very loosely, stretching the edge as you go.