Abstract: The disclosure is that of an invention directed to a folder for a continuously advancing web of textile material in which a transverse guide roll assembly provided with a pair of parallel guide rolls is bodily reciprocated horizontally along a supporting frame. The guide rolls are positively driven in the same opposed directions at all times; and the speed of bodily reciprocation of the guide roll assembly is progressively reduced as that assembly approaches the end of each stroke of reciprocation in order to avoid a slack or bunched condition of the web in the central portion of each fold.