13 a plurality of tensioning strings 2 only one of which is shown in fig1 which are to be coupled individually to an auxiliary warp thread 1 are guided around a cross bar 3 in the form of a gallows and are held under constant tension by weights 4 the weights 4 may have the form of small rods of 12 g mass since up to 448 tensioning strings 2 may be tightened simultaneously the weights 4 consist of stainless steel and are each provided with an eye on top for threading the associated tensioning string 2 the ends of the tensioning strings 2 are threaded through squeeze tubelets 5 above the weights 4 which are then tightened by clamping in order to prevent entanglement of the great number of weights 4 and to keep them mobile and in good order the individual weights are guided through two perforated plates 6 screwed to the cross bar 3 before they are introduced into the weight box 7 provided for protection against external influences each tensioning string 2 weighted down by a weight 4 is diverted to a horizontal plane by a grid 8 of known design and is guided toward a storage plate 9 secured to the front end of the horizontal portion of the gallows like bar 3 the storage plate 9 has a bore 14 for each tensioning string 2 to be coupled to an auxiliary warp thread 1 for receiving a coupling means 13 in the storage plate 9 the bores 14 are arranged in eight horizontal rows of 56 individual bores each each coupling means 13 includes a guide sleeve 10 having for example an external diameter of 1 mm and an overall length of 22 mm for an auxiliary warp thread 1 having a.