Cast-on an odd number of stitches.
Set-Up Row (WS): *K1, P1* last stitch, K1
Row 1 (RS): K1, *K1B, P1* last 2 stitches, K1B, K1
Row 2 (WS): K1, *P1, K1B* last 2 stitches, P1, K1
Repeat rows 1-2 until desired length.
Ending on a right side row.
With the wrong side facing you, bind-off in the K1, P1 rib stitch.
Weave in the ends.
Gently block or steam-block lightly, if desired.