Using a US6/4mm needle, cast on 80 stitches. I used cotton yarn.
Row 1: Knit placing a stitch marker after 40 stitches (at the halfway point)
Row 2: Knit to two stitches before the stitch marker, knit two stitches together, slip the stitch marker to the other needle, slip slip knit, knit to the end of row.
Repeat rows 1 and 2 until two stitches remain. Repeat row 1 once more. Cast off.