A quill of yarn is a cover for a spindle, onto which thread or yarn is wound; it can then be easily removed for use. Mundanely, it’s also known as an “embroiderer’s quill”. The blazon should include reference to yarn or embroidery, to help distinguish it from a “quill pen”.
The quill of yarn is a period charge, dating to 1558 in the arms of the Worshipful Company of Broderers [Bromley & Child 31]. It’s palewise, and wound with yarn, by default. There are instances in mundane armory of empty quills, without yarn, such as the arms of von Haren, 1605 [Siebmacher 147], but the fact is always blazoned.
The “spindle” itself is also found, the winding piece of a spinning wheel. It’s drawn as a slender cone wound with thread or yarn; it’s found in the arms of Hobby, 1610 [Guillim1 204], where it’s blazoned as a “fusile upon a slipper”.
Katharina die Schneiderin bears: Vert, a bend wavy between two quills of yarn Or.
Molda ókristna Starradottír bears: Vert, three yarn quills argent threaded Or.
Maud verch Howell bears as a badge: Per bend sinister sable and argent, on a bend counterchanged, two spindles palewise gules and Or.