wide mock rib

RT K2tog leaving sts on LH needle, insert RH needle from front between 2 sts just knitted tog and k first st again, then sl both sts from needle tog.
(multiple of 9 sts plus 2)
Row 1 (WS) K1, *p4, k5; rep from *, end k1.
Row 2 P1, *p5, RT twice; rep from *, end p1.
Row 3 Rep row 1.
Row 4 P1, *p5, k1, RT, k1; rep from *, end p1.
Rep rows 1–4.