the stop disk the actuator is preferably a stepping motor and the adjusting cam preferably has a spiral shape application_number US 70399996 A description referring to the drawings in particular the invention comprises a guide rail 2 for a carriage 3 that can be moved along on the said guide rail is fastened to a support plate 1 a folding rail 4 comparable to the folding rail disclosed in de 80 27 080 u1 is detachably fastened to the carriage 3 like the prior art folding rail the folding rail 4 is adjustable in a manner not specifically explained here and is also interchangeable with other folding rails having a different shape and different dimensions together with the folding rail 4 the carriage 3 can be moved to and from by means of a compressed air cylinder 5 between an inserting position shown in the drawing and a working position in which the folding rail 4 places the fabric to be provided with a fold in the correct position for sewing under a feed rail not shown the desired tuck depth of the fold or of a tuck which are to be formed depends on the shape and width of the folding rail 4 and is additionally determined by.