Before wool can be spun it is necessary to comb, or card, it to align the fibers and remove knots and debris. Today that job is done very efficiently by machine, but before mechanization, of course, it had to be done by hand. Wool cards are steel brushes that look very much like large dog or cat brushes. There was another “tool”, however, that made use of a plant , “fuller’s teasel.” Related to thistles, teasel develops a prickly seed head that when dried can be used much as a card to comb wool. There were wooden tools available to which a number of the seed heads could be attached. (See link in comment below). Teasel was also widely used, as its name suggests, by fullers, those craftsmen who shrunk woven cloth and raised the nap, thereby “finishing” it. The term “tease”, as in teasing one’s hair, is derived from this source.
See comment below for a website link to this process, with pictures. Thank you to saesford for this info.