Reversible cable stitch.
Abbreviations:
3/3 RPC – 3 over 3 right purl cross – slip 3 stitches onto a cable needle and hold in the back, k3, p3 from cable needle.
Multiples of 6 plus 9
Row 1 (WS): p3, [k3,p3] 6 times, k6
Rows 2-5: Work stitches as they present themselves, knit the knits and purl the purls.
Row 6 (RS): p3, [3/3 RPC] 6 times, k6
Rows 7-15: Work stitches as they present themselves, knit the knits and purl the purls.
Row 16: p6, [3/3 RPC] 6 times, k3
Rows 17 -20: Work stitches as they present themselves, knit the knits and purl the purls.
Rep rows 1-20 for pattern
Chart:
