2 do not appear as areas of error the clamping jaws 3 a 3 b are arranged on continuously driven belts 10 a 10 b with which they each can be returned to the false twisting unit 8 furthermore the clamping jaws 3 a 3 b can in this manner be turned on and off in the area lying between the belts 10 a and 10 b opposing pairs of clamping jaws 3 a 3 b are pressed against one another with the inter positioning of the yarn 1 u2032 to form then a twisting stop 3 movable in the yarn advancing direction c the movable twisting stops 3 are spaced apart at a distance l 2 the twisting stops 3 are moved through a fixing unit 11 which consists of a heating zone 4 and a downstream oriented cooling zone 5 the spaced apart distance l 2 of the twisting stop 3 is thereby less than the length l 3 of the fixing unit 11 it is assured in this manner that the twists alternately oppositely applied to the yarn 1 u2032 and temporarily fixed between two twisting stops 3 are thermally fixed when the finished filament yarn 1 leaves the fixing unit 11 in order for the method to operate as effectively as possible the twisting stops 3 should engage the yarn 1 u2032 to stop the twisting as close as possible to the false twisting unit 8 and should then be advanced synchronously with the yarn 1 u2032 with each new engagement of the yarn by.