The hummeller was stamped onto piles of grain and twisted. This action helped to separate the bristles and husks from the grain.
Humellers could have round, square or oblong frames, with iron bars riveted inside the frame. Some, such as the one pictured (Slight and Burn, 1858, p. 491), had the internal bars crossing each other to form small square compartments. A version with parallel bars only is found at Brickendon — while this was considered less effective it was also cheaper.