the beat up lamellae or elements 12 the warp threads 4 shown by a double line located in each case in the upper shed position in the lamellae reed 11 1 which has dipped already for some time into the warp threads are guided by the rods 17 1 on the other hand the warp threads 4 shown with a single line are located in the lamellae reed 11 1 in each case in the lower shed position and are guided by the rods 17 2 as already stated for reasons of clarity in illustration both of the other rods 17 shown in fig1 have been omitted so that in the lamellae reed 10 each second tube does not have any warp thread 4 and in the lamella reed 11 each tube only has one warp thread 4 it is assumed that the lamellae reed 10 as well as the lamellae reed 11 1 have completely dipped into the warp threads 4 and that the lamellae reed 11 2 will shortly dip into the warp threads 4 and the warp threads 4 guided by the rods 17 1 should reach the lower shed position and the warp threads 4 guided by the rods 17 2 should reach the upper shed position to achieve this result the rods 17 1 and 17 2 must be moved by the actuation device 18 fig2 in such a manner that the warp threads 4 guided by such rods must assume the position illustrated in full lines the warp threads 4 guided by the rod 17 1 are thus moved towards the left and the warp threads 4 guided by the rod 17 2 are moved towards the right until they bear at the beat up lamellae 12 which.