A picot edge is a zig-zag trim. It also prevents the edges of stockinette stitch from curling. 

1. Cast on the required number of stitches. Work in stockinette stitch for odd number of rows (3 or 5).

2. Next row: Facing WS, *yo, k2tog, rep from *. This will create an eyelet row. 

3. Work in stockinette stitch for the same number of rows as before the eyelet row (3 or 5).

4. Facing WS, fold the piece at the eyelet row. Carefully sew the cast-on row to the piece.

5. The picot edge is finished. Work your piece as normal.