I found this:
With a different coloured yarn cast on half the stitches plus 2 for ends. With the yarn of the work, work as follows:
Row 1 - * k 1., yo.* Repeat from * to *.
Row 2 - k1 end st. *kl into yo., slip purled st. *. Repeat from * to * k 1 end st.
Row 3 - k1 end st. * k1 ., slip purled st. *. Repeat from * to * k1 end stitch
Repeat Row 3 for rib height required.