Shown with a cast-on count of 21 stitches.  

• Row 1 (RS): K21.
• Row 2: K10, M1L, p1, M1R, k10 (23 sts).
• Row 3: K11, M1R, k1, M1L, knit (25 sts).
• Row 4: K12, M1L, p1, M1R, knit (27 sts).
• Row 5: K13, M1R, k1, M1L, knit (29 sts).
• Row 6: K14, M1L, p1, M1R, knit (31 sts).
• Row 7: K15, M1R, k1, M1L, knit (33 sts).
• Row 8: K16, M1L, p1, M1R, knit (35 sts).
• Row 9: K17, M1R, k1, M1L, knit (37 sts).
• Row 10: K18, M1L, p1, M1R, knit (39 sts).
• Row 11: K19, M1R, k1, M1L, knit (41 sts).
• Row 12: Knit.
• Row 13: K20, MB, k20.