In the past, 'Hoso-Udon' (literally, thin Udon noodles) and 'Hiyamugi,' both of which are thin noodles, were clearly distinguished by the differences in the manufacturing process (whether the dough is stretched by a rolling pin or machine before cutting, whether the dough is molded into cylindrical shape before stretching, and others), as well as by the social notion.
かつては製法の違い（麺棒や機械で生地を伸ばしてから切るか、細く丸めた生地を引いて伸ばすか等）、社会通念上も、細い麺の「細うどん」と「ひやむぎ」は明確に区別されていた。