To knit this design
Using Dark cast on 41 stitches. Knit one row, placing markers every ten stitches. This is your first ridge.
Ridge 2 (Light) : Knit the first row and purl the second.
Ridge 3 (Dark) : Knit both rows.
Ridge 4 (Light) : Knit the first row and purl the second.
Ridge 5 (Dark) : Knit both rows.
Ridge 6 (Light) : Knit the first row and purl the second.
Ridge 7 (Dark) : Knit the first row. On the second row, knit the coloured stitches and purl the white stitches.
The chart shows k17, p7, k17
Ridge 8 (Light) : Knit the first row. On the second row knit the coloured stitches and purl the white stitches.
The chart shows p17, k7, p17
Continue following the chart in this way, changing colour for each ridge. Cast off on the last row.