A scalloped sideways knitted edging with I-cord top edge & a rolling purl stitch lower edge surrounding a semicircle of garter stitch formed using a combination of rapid increases, short rows & decreases. You can knit it as long as you like or need.

The pink edging in the photo is knitted in DK yarn on 4mm needles. 4 scallops measure 6 1/4 inches. 1, 50g ball of Patons Diploma Gold creates 41 scallops..