points of this triangular area are visible in fig1 and this area determines the working field for the longitudinal movement of the harnesses 41 42 it being understood that the section for the rotor 47 which is shown in fig1 is located approximately in the working plane 49 of the needle 17 one of the corner points of the triangular area is determined by the one lateral position 56 39 of the eye for the filament 15 whereas the other corner point of the triangular area is determined by the diametrically opposite position 15 34 of the filament 15 when this eye is located in the position designated with reference numeral 56 34 in fig1 the triangular area is therefore determined by the points 56 39 56 34 and 57 and the harnesses 41 42 of which more than the illustrated four may be present operate within this area assuming that a zipper is produced of the type that is to be used in a garment then as a rule it will be customary to use eight of the harnesses 41 42 since eight of the threads 18 19 would be employed if the element 60 is centrally located with respect to the.