Janome Hemmer Foot D 2mm Cat B/C

The hemmer foot, sometimes referred to as the rolled hemmer is used to stitch the narrow rolled hems usually found on shirt tails, table linens and along the edge of frills.
The hemmer is designed with a scroll shaped feeder on top and a straight groove on the underside which determines the width of the finished hem.

The standard 2mm hemmer foot is for lightweight fabrics. 

There are 4mm and 6mm hemmer feet too, which are for medium to heavier fabrics and are available separately.