Feed dogs are metal teeth-like ridges that emerge from a hole in the throat plate of a sewing machine. Feed dogs gently grip the underneath of the fabric, coaxing it to move away from the needle as stitches are sewn.
While most sewing is done with the feed dogs up, darning and freehand quilting are performed with the feed dogs either down or covered. Putting feed dogs in the down position eliminates the machine's grip on the underside of the fabric, placing the quilter in full control of the movement of fabric.
An even feed foot, also called a walking foot, has built-in feed dogs at its base, and is helpful when sewing multiple layers of fabric. The foot's feed dogs move the upper layer of fabric at the same rate as the machine's feed dogs advance the lower layer.