A quill pen is made from a flight feather (preferably a primary) of a large bird, most often a goose. Quills were used as instruments for writing with ink before the metal dip pen, the fountain pen, and eventually the ball point pen came into use.
Common writing equipment in medieval times were the quill and parchment (equivalent to later times' pen and paper). The hand-cut goose quill is still a superior calligraphy tool, providing a sharp stroke and flexibility unmatched in steel pens.
A signwriter or sign painter uses a "quill" brush as a main tool. The quill brush is usually made from ox hair, which is more durable than many other artist brushes. It has a quill ferrule which attaches the hair to the brush handle and is tied together with wire.