Known as a Walking Foot,the Singer Even Feed Foot for drop in bobbin machines is designed with a set of feed dogs.
 
When sewing these feed dogs grab the fabric on the top, whilst the feed dogs of the machine grabd the fabric underneath.
 
This ensures that both the top and bottom fabrics are feed evenly through the machine thus preventing fabric layer from sipping or creeping forward.
 
Ideal for quilting, multiple layers, curtain making, sewing thicker or tricky fabrics.
 
Fits modern drop in bobbins machine - eg: Singer Heavy Duty range