A double cable (or horseshoe cable) looks intricate but is easy to knit. Try knitting this sample panel of double cable. The panel is 18 stitches (the cable is 12 stitches wide with 3 set-up stitches on either side of it).
Knit this double cable (horseshoe cable) pattern:
Cast on 18 sts.
Follow this stitch pattern:
Rows 1 and 3 (RS): P3, k12, p3.
Rows 2, 4, and 6: K3, p12, k3.
Row 5: P3, sl next 3 sts to cn and hold in back, k3, k3 from cn, sl next 3 sts to cn and hold in front, k3, k3 from cn, p3.
Repeat Rows 1–6.
A double cable is really nothing more than a right cable next to a left cable. You can turn the cable upside down by working a left cable first and then a right one.