Feed dogs

The feed dogs are the “teeth” you see moving back and forth under the throat plate of the sewing  machine or serger (overcast or merrow machine). Their purpose is to move the fabric back, forth, or even sideways as it is sewn. Some sergers with “differential feed” have split feed dogs, two pair instead of a single pair, that can vary the amount of push and pull on the fabric. This handy feature allows the machine to handle difficult fabrics with ease.