The overcast foot is also known as an over-edge or overlocker foot.
It is a magical little sewing machine foot that can give you an edging similar to that of an overlocker with just about any sewing machine.
This is a really simple to use foot, when you have the correct stitch selected.
Using a stitch similar to the one in the image, you need to select a stitch which jumps out to the edge of the fabric as this is what binds the edges to secure them.
As a general rule, those stitches that move only forward are better for light-medium weight fabrics, whereas those that move back and forwards are better suited to medium - heavy weight fabrics.
You might want to experiment to see what works best with your machine.
The overcast foot works by having a bar in the centre which wraps the thread around the edge of the fabric as you stitch, whilst preventing the fabric from curling.
Clip the foot onto your sewing machine with the bar attachment.
Line your fabric edge up against the guide and select either an over-edge stitch or a wide zigzag stitch.
Always check that the needle won't hit metal in the centre bar with the stitch you have selected.
Manually hand crank a couple of stitches first just to be sure.
Then sew on down the raw edge of the fabric to secure your edges.