Old Shale Lace Pattern

Pattern
Cast on a multiple of 18 stitches
Row 1 (RS): Knit.
Row 2 (WS): Knit.
Row 3: Purl.
Row 4: Knit
Row 5: *[K2tog] 3 times, [Yo,K1] 6 times, [K2tog] 3 times; rep from *.
Row 6: Purl.
Row 7: *[K2tog] 3 times, [Yo,K1] 6 times, [K2tog] 3 times; rep from *.
Row 8: Purl.
Row 9: *[K2tog] 3 times, [Yo,K1] 6 times, [K2tog] 3 times; rep from *.
Row 10: Purl.
Row 11: *[K2tog] 3 times, [Yo,K1] 6 times, [K2tog] 3 times; rep from *.
Row 12: Purl.
Repeat rows 1-12.