for pulling the other end of the chain for separating the holding elements in order to spread out the workpiece application_number US 87622486 A description fig1 and 5 show a guide rail 2 according to a first embodiment of the invention which is connected displaceably in a known manner to a sewing machine for instance an automatic long seamer for defining the instance an automatic long seamer for defining the desired course of a seam the workpiece is placed on the work table and displaced by the guide rail 2 and is thus moved past the stitch formation point of the sewing machine the bottom 1 of the guide rail 2 has a groove 10 which extends parallel to its longitudinal edges fig6 is an elevational view of a sewing machine equipped with a guide rail 2 according to an embodiment of the invention as seen therein the guide rail reciprocates between two extreme positions the position in solid lines at the right of fig6 is occupied by the guide rail prior to a sewing operation and will be referred to as the 34 forward 34 position the position at the left of fig6 shown in phantom will be referred to herein as the 34 rearward 34 position as the guide rail moves from the forward position to the rearward position the entire workpiece is moved past the stitch formation point of the sewing machine a sewing material stretching device 3 on the bottom 1 comprises a plurality of holding elements 4 arranged in an overlapping manner one behind the other each of the holding.