Using the smooth yarn, make a foundation chain of the required length, or work row 1 directly into the item to be trimmed with right side facing.

(odd number of stitches)

Row 1: (smooth yarn) 1 ch, 1 sc in each st or position to end. Fasten off, turn.
Row 2: (fluffy yarn) 3 ch, *2 dc in next st, 1 dc, rep from * to end, turn.
Row 3: (fluffy yarn) As row 1. Fasten off, turn.
Row 4: (smooth yarn) As row 1. Fasten off.